Preheat the oven to 350°F (175°C) and lightly grease a baking pan.

Combine the ground beef, chopped onion, diced bell pepper, diced tomato, egg, minced garlic, and seasoned bread crumbs in a large bowl.

Press half of the meat mixture into the prepared baking pan, creating a base layer.

Layer the Muenster cheese slices evenly over the meat base.

Add the remaining meat mixture on top, pressing gently to form an even layer.

Spread the prepared mashed potatoes over the top of the meatloaf cake.

Sprinkle shredded cheddar cheese over the mashed potatoes.

Bake for 45–55 minutes, or until the meat is fully cooked and the cheese is melted and golden.

Let the meatloaf cake rest for 5–10 minutes before slicing and serving.