If you don’t have pre-made blackening seasoning, mix paprika, cayenne pepper, garlic powder, onion powder, dried thyme, dried oregano, salt, and black pepper to create the seasoning.
Pat the fish fillets dry with paper towels. Drizzle both sides with olive oil and sprinkle the blackening seasoning generously on all sides, pressing it into the fish.
In a small bowl, whisk together mayonnaise and lemon juice. Add salt and pepper to taste to make the lemon mayo spread.
Heat a large skillet over medium-high heat with a drizzle of olive oil. Cook the seasoned fish fillets for 3-4 minutes per side until blackened and flaky. Avoid moving the fish too much.
While the fish cooks, slice the buns in half and toast them lightly in a toaster or skillet until golden and slightly crisp.
Spread lemon mayo on the bottom half of each bun. Top with shredded lettuce, sliced tomato, and the hot blackened fish fillet. Finish with the top bun and press gently.
Serve immediately with your favorite sides like sweet potato fries, salad, or coleslaw for a delicious meal.