Preheat your oven to 350°F (175°C).
In a large skillet, brown the ground beef over medium heat.
Add diced onions and garlic, sautéing until translucent.
Stir in carrots and bell peppers, cooking for another 5 minutes.
Mix in the peas and diced tomatoes, letting the mixture simmer for 5 minutes.
Combine the cooked rice with the beef mixture.
Season with salt and pepper to taste.
Transfer the mixture to a baking dish and spread evenly.
Top with shredded cheese.
Bake for 20 minutes, or until the cheese is bubbly and golden.