Prep Time: 15 minutes | Cook Time: 10 minutes | Total Time: 25 minutes | Servings: 4
- Perfect for weeknight dinners – ready in just 25 minutes from start to finish
- Restaurant-quality meal at a fraction of the cost
- Customizable heat level – adjust spices to suit your family’s preferences
- Loaded with heart-healthy omega-3s from fresh swordfish
Why You Need These Blackened Swordfish Sandwiches Now
Ever tried making fish sandwiches at home only to end up with soggy bread and bland fish? Not anymore.
These blackened swordfish sandwiches deliver bold Cajun flavors with the perfect sear on the outside while keeping the fish moist and tender inside. No more boring fish dinners!
Nutrition Facts Per Serving
| Nutrient | Amount | % Daily Value |
|---|---|---|
| Calories | 420 | – |
| Protein | 32g | 64% |
| Fat | 18g | 28% |
| Carbohydrates | 32g | 11% |
| Fiber | 3g | 12% |
| Sodium | 680mg | 28% |
| Omega-3 | 1.2g | 120% |
What You’ll Need
Ingredients
| Ingredient | Amount | Notes |
|---|---|---|
| Swordfish steaks | 1½ pounds (4 steaks, about 6 oz each) | ¾-inch thick |
| Cajun blackening seasoning | 3 tablespoons | Store-bought or homemade |
| Olive oil | 2 tablespoons | For brushing fish |
| Brioche buns | 4 | Split and lightly toasted |
| Mayonnaise | ½ cup | – |
| Fresh lemon juice | 1 tablespoon | About half a lemon |
| Garlic | 1 clove | Minced |
| Hot sauce | ½ teaspoon | Adjust to taste |
| Butter lettuce | 4 large leaves | – |
| Tomato | 1 large | Sliced |
| Red onion | ½ small | Thinly sliced |
| Butter | 2 tablespoons | For toasting buns |
| Fresh parsley | 2 tablespoons | Chopped (optional) |
Kitchen Tools
| Tool | Purpose |
|---|---|
| Heavy cast-iron skillet | For blackening the fish |
| Fish spatula | For flipping delicate fish |
| Mixing bowl | For sauce preparation |
| Measuring spoons | For accurate seasoning |
| Cutting board | For preparation |
| Sharp knife | For slicing vegetables |
| Kitchen timer | To ensure perfect cooking time |
| Meat thermometer | Optional but recommended |
Ingredient Substitutions
- Fish Options: Mahi-mahi or tuna steaks work well in place of swordfish
- Bun Alternatives: Whole wheat buns, ciabatta rolls, or even lettuce wraps for low-carb
- Dairy-Free: Use vegan mayonnaise and plant-based butter
- Gluten-Free: Choose gluten-free sandwich buns
Beginner-Friendly Step-by-Step Instructions
Preparation Phase (15 minutes)
- Gather your ingredients and tools:
- First, take out all ingredients from the refrigerator and pantry
- Arrange them on your counter so everything is within reach
- Set up your cutting board and knife in a comfortable workspace
- BEGINNER TIP: Measuring all ingredients before starting (called “mise en place”) makes cooking much easier
- Prepare the swordfish:
- Remove swordfish from packaging and place on a clean plate
- Using paper towels, gently pat each steak completely dry on both sides
- Look for any dark portions (bloodline) or skin and remove these with a sharp knife
- BEGINNER TIP: Removing moisture helps the seasoning stick better and creates a better sear
- Let fish sit at room temperature for 15 minutes (this helps it cook more evenly)
- Make the special sauce:
- Select a small mixing bowl
- Measure ½ cup mayonnaise and add to the bowl
- Cut a lemon in half and squeeze to extract 1 tablespoon of juice (about half a lemon)
- BEGINNER TIP: Squeeze lemon over a separate small bowl to catch seeds
- Peel 1 garlic clove and mince it very finely (tiny pieces) with your knife
- Add minced garlic to the mayo mixture
- Add ½ teaspoon hot sauce (or less if you prefer milder flavor)
- Using a spoon, mix all ingredients together until completely smooth
- Cover bowl with plastic wrap and place in refrigerator
- Prepare your vegetables:
- Fill a bowl with cold water
- Separate 4 large butter lettuce leaves, rinse in the water, then pat dry with paper towels
- Place lettuce on a clean plate
- Rinse tomato under cold water and pat dry
- Place tomato on cutting board and carefully slice into ¼-inch thick rounds (you’ll need 4-8 slices)
- BEGINNER TIP: Use a serrated knife for tomatoes if you have one
- Cut off ends of red onion and remove outer skin
- Cut onion in half from top to bottom and place flat side down on cutting board
- Slice half the onion into very thin slices (paper-thin is best)
- Place vegetables on a plate and set aside
- Season the fish:
- Place swordfish steaks on a clean plate or cutting board
- Pour 2 tablespoons olive oil into a small bowl
- Using a cooking brush or your fingers, coat both sides of each swordfish steak with a thin layer of olive oil
- BEGINNER TIP: The oil helps the seasoning stick and prevents fish from sticking to the pan
- Measure 3 tablespoons of Cajun blackening seasoning into a small bowl
- Sprinkle seasoning evenly over one side of each steak (about ¼ tablespoon per side)
- Using your fingers, gently press seasoning into the fish to help it adhere
- Flip steaks over and repeat on the other side
- Let seasoned fish rest for 5 minutes to absorb flavors
Cooking Phase (10 minutes)
- Prepare your cooking area:
- Open windows or turn on exhaust fan (blackening creates some smoke)
- BEGINNER WARNING: Make sure to have good ventilation before starting to cook
- Have a clean plate ready for the cooked fish
- Keep your fish spatula nearby
- Place cast-iron skillet on stovetop burner
- Heat your skillet properly:
- Turn burner to medium-high heat
- Allow skillet to heat for 3-4 minutes (this is important for proper blackening)
- BEGINNER TIP: Test if pan is hot enough by sprinkling a few drops of water on the surface – they should sizzle immediately and disappear
- BEGINNER WARNING: Pan will be extremely hot – do not touch the surface or handle without protection
- Toast the buns:
- While skillet is heating, place a separate frying pan on another burner over medium heat
- Add 2 tablespoons butter to the pan and let melt completely
- Split each brioche bun with a knife if not pre-split
- Place buns cut-side down in the melted butter
- Toast for 1-2 minutes until golden brown (peek underneath to check)
- BEGINNER TIP: Don’t walk away – buns can burn quickly
- Remove toasted buns to serving plates, placing them open-faced and ready for assembly
- Cook the swordfish (most important step):
- Once skillet is very hot, carefully place seasoned swordfish steaks in the pan
- BEGINNER TIP: If all steaks don’t fit with space between them, cook in batches of 2
- Let cook undisturbed for 3-4 minutes (resist the urge to move them)
- Look for a dark crust forming on the bottom edge and the sides of fish turning opaque about ¼ of the way up
- Using your fish spatula, carefully flip each steak over
- BEGINNER TIP: If fish sticks to pan, it may not be ready to flip – wait 30 more seconds
- Cook second side for 2-3 minutes until internal temperature reaches 145°F on meat thermometer
- BEGINNER TIP: If you don’t have a thermometer, check that fish is opaque throughout but still looks moist
- Remove fish from pan immediately to prevent overcooking
- Place on clean plate and let rest for 2 minutes before assembling sandwiches
Assembly Phase (5 minutes)
- Build your sandwiches (bottom to top):
- Take bottom half of toasted bun
- Spread 1 tablespoon of prepared sauce evenly over the bread
- Place a butter lettuce leaf on top of sauce (this creates a barrier to prevent soggy bread)
- Carefully place one blackened swordfish steak on top of lettuce
- Add 1-2 tomato slices on top of fish
- Place 3-4 thin red onion slices on top of tomato
- BEGINNER TIP: If you prefer less onion flavor, soak slices in ice water for 5 minutes and pat dry before using
- Spread another tablespoon of sauce on the inside of the top bun
- Place top bun on sandwich
- Optional: Secure with a toothpick to hold together
- For easier eating, cut sandwich in half using a serrated knife
- Final presentation:
- Arrange sandwiches on plates with cut side facing out to show layers
- Add a small side of any remaining sauce for dipping
- Sprinkle with fresh chopped parsley if desired
- Serve immediately while fish is still warm and buns are crisp
Troubleshooting
| Problem | Solution |
|---|---|
| Fish sticks to pan | Make sure pan is fully heated before adding fish and fish is patted completely dry. Add a little more oil to the pan if needed. |
| Too spicy | Reduce blackening seasoning by half; serve with extra mayonnaise or add a teaspoon of honey to the sauce to balance heat. |
| Too dry | Cook for 1-2 minutes less; swordfish cooks quickly and continues cooking after removal from heat. |
| Buns too soggy | Toast buns more thoroughly; always place lettuce between fish and bun to create a moisture barrier. |
| Blackening seasoning burning | Lower heat slightly and continue cooking; some blackening is expected and adds flavor. |
Variations & Substitutions
Cajun-Style
- Add ¼ cup finely diced bell peppers to mayonnaise
- Include ½ teaspoon of cajun seasoning in mayo
- Top with pickled jalapeños
Mediterranean Version
- Replace mayo with tzatziki sauce
- Add sliced cucumbers and feta cheese
- Use oregano and lemon zest in seasoning
Asian-Inspired
- Make wasabi mayo (add 1 teaspoon wasabi paste to mayo)
- Top with quick-pickled carrots and cucumber
- Substitute some blackening spice with Chinese five-spice
Storage & Reheating
Leftover Storage
- Cooked fish: Refrigerate in airtight container up to 2 days
- Sauce: Keep refrigerated up to 5 days
- Store components separately for best results
Reheating Instructions
- Gentle reheating: Place fish in 300°F oven for 8-10 minutes
- Avoid microwave as it can make fish rubbery
- Reassemble sandwich with fresh vegetables after reheating
Safety Notes & Tips
Food Safety
- Always cook swordfish to an internal temperature of 145°F
- Keep raw fish refrigerated until ready to cook
- Wash hands thoroughly with soap for 20 seconds after handling raw fish
- Sanitize all surfaces that come in contact with raw fish
- Don’t reuse plates or utensils that touched raw fish without washing
Recipe Tips
- Don’t overcook – swordfish can dry out quickly; when in doubt, slightly undercook as it will continue cooking after removal from heat
- Even thickness – ensure steaks are uniform thickness for even cooking; ask your fishmonger to cut them evenly
- Proper heat – blackening requires high heat; expect some smoke, which is normal for this cooking method
- Ventilation – open windows or use exhaust fan when blackening to prevent smoke alarm activation
- Seasoning balance – blackening spice can be intense; start with less if you’re sensitive to spice
- Room temperature fish – taking fish out of refrigerator 15 minutes before cooking helps it cook more evenly
- Fresh fish matters – for best results, purchase swordfish the day you plan to cook it
Chef’s Notes
For the ultimate blackened swordfish sandwich, let the fish rest 2-3 minutes before assembling. This allows juices to redistribute throughout the fish, keeping it moist while firming the flesh for better handling.
The mayo sauce can be made a day ahead to save time and allow flavors to blend.
If serving kids, you might want to reduce the spice level and offer the sauce on the side.
Perfect side dishes for these sandwiches include sweet potato fries, coleslaw, or a simple green salad with lemon vinaigrette.
