Preheat the oven to 350°F (175°C) and lightly grease a 9×13-inch casserole dish.
In a large skillet or Dutch oven over medium heat, cook the chopped onion and green peppers in the avocado oil until tender, about 5–6 minutes.
2 tablespoons avocado or neutral oil, 2 green bell peppers, ½ onion, chopped
Add the ground beef to the pan with the vegetables and cook until browned, breaking it apart with a spoon. Drain off excess fat if needed.
1 pound ground beef, 80/20
Stir in the diced tomatoes with their juice, tomato sauce, Karo syrup, bay leaf, chili powder, salt, and pepper. Reduce the heat to low and let the sauce simmer for 15 minutes, stirring occasionally.
¼ cup tomato sauce, 12 ounces diced canned tomatoes with juice, ½ cup dark Karo syrup, 1 teaspoon chili powder, 1-2 bay leaves, salt & pepper
While the sauce simmers, bring a large pot of salted water to a boil. Cook the macaroni 2 minutes less than the package instructions for al dente, then drain and set aside.
8 ounces macaroni noodles
Remove the bay leaf from the sauce and stir in the cooked pasta until well coated.
Pour the pasta and sauce into the prepared casserole dish and sprinkle the shredded cheddar cheese evenly over the top.
1 cup cheddar cheese
Bake for 30 minutes, or until the cheese is melted, bubbly, and slightly golden.
Let the casserole rest for about 5 minutes before serving.