Sprinkle fillet with lemon juice, salt and pepper. Coat with cornmeal and set aside. In a skillet, cook bacon over medium heat until crisp. Remove to paper towels; drain, reserving 2 tablespoons drippings.
In the same skillet, cook fillet in reserved drippings for about 4 minutes on each side or until fish flakes easily with a fork. Meanwhile, butter cut sides of buns. Place buttered side up on a baking sheet. Toast under broiler for about 1 minute or until golden brown. In a small bowl, combine mayonnaise and garlic; spread on buns. Top with lettuce, tomato slices and fish.