In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the finely chopped onion, cooking for about 3-4 minutes until it turns translucent. Next, toss in the minced garlic, diced carrots, and bell peppers, stirring frequently for another 5-7 minutes until the vegetables are tender yet crisp.

Push the sautéed vegetables to the side of the skillet and add 1.5 lbs of lean ground beef. Brown the beef for about 5-7 minutes, breaking it apart with a spatula until there’s no pink remaining. Carefully drain any excess fat from the skillet.

Stir in 2 cups of tomato sauce, 1 can of drained diced tomatoes, and 1 cup of beef broth. Sprinkle in 2 teaspoons of Italian seasoning, along with salt and pepper to taste. Allow the mixture to simmer on low heat for 10 minutes.

Preheat your oven to 375°F (190°C). Pour the beef and vegetable mixture into a greased casserole dish. Top with 1 cup of shredded mozzarella or Parmesan cheese and ½ cup of breadcrumbs.

Bake for 25-30 minutes, or until the cheese is melted, bubbly, and golden brown. Let it cool for 5-10 minutes before serving.