Heat 2 tablespoons of olive oil in a large skillet over medium heat. Add 1 finely chopped large onion and sauté for about 3-4 minutes until translucent.

Incorporate 4 minced garlic cloves, 2 diced medium carrots, and 1 diced red and 1 diced yellow bell pepper, continuing to cook for an additional 5-7 minutes until the vegetables are tender and aromatic.

Push the vegetables to the side of the skillet and add 1.5 pounds of lean ground beef into the center. Break apart the beef with a spatula, browning it thoroughly for about 5-7 minutes.

Drain any excess fat to retain a healthy balance in the casserole.

Stir in 2 cups of tomato sauce, 1 drained can of diced tomatoes, and 1 cup of beef broth. Sprinkle in 2 teaspoons of Italian seasoning, adjusting with salt and pepper to taste.

Allow the mixture to come to a simmer, letting the flavors meld together for 10 minutes while stirring occasionally.

Preheat your oven to 375°F (190°C) and prepare a casserole dish.

Pour in the beef and vegetable mixture, spreading it evenly across the bottom. Sprinkle 1 cup of shredded cheese on top, along with optional ½ cup of breadcrumbs.

Place the casserole in your preheated oven and bake for 25-30 minutes, or until the cheese is bubbly and golden brown.

Let it cool for 5-10 minutes before serving to enhance the flavors.