Preheat oven to 375°F. Bring pan to medium heat.

Rub tilapia with cayenne pepper, black pepper, and 1/2 tsp garlic powder. Add to frying pan and cook until at least 150°F.

Wash veggies. Slice two rings of yellow pepper, 4 slices of tomato, and 2 slices of onion. Cut 1 slice of onion in half, and set half aside.

Spread butter across bread. Cover butter with pepperjack cheese, top with tomato slices, yellow pepper, and onion rings.

Remove tilapia from frying pan. Set on top of veggies, and place in oven for 12-14 minutes.

Combine mayonaisse, 1/4 tsp garlic powder, relish, and 1/2 slice of diced onion. Mix together and serve on the side of sandwich.