Prepare a medium grill or preheat the broiler.

If using the broiler, line a rimmed baking sheet with aluminum foil.

Make the tartar sauce: In a small bowl, combine mayonnaise, chopped sweet pickles, chopped red onion, freshly squeezed lemon juice, and garlic powder.

Cover and refrigerate the tartar sauce until ready to use.

Brush the tilapia fillets with olive oil and season with salt and pepper.

Cut the French bread into four 7-inch sections and cut each section in half lengthwise.

Place the tilapia on the grill or, if broiling, place on the prepared baking sheet.

Grill or broil the tilapia, 4 inches from the heat, turning once, for about 6 minutes total, or until the tilapia flakes easily with a fork and is cooked through.

Lay the bread on the grill or broiler cut side down and grill or broil for about 1 minute, or until toasted.

Assemble each poboy: Place 1 grilled tilapia fillet on the bottom slice of bread.

Top the tilapia with 2 slices of tomato and 1 romaine lettuce leaf.

Spread the top slice of bread with 2 tablespoons of tartar sauce.

Place the tartar sauce-covered bread on top of the sandwich.