In a skillet over medium heat, cook the ground beef until browned. Drain excess fat.
Add the chopped onion and minced garlic to the skillet. Sauté until the onion is translucent, about 3-5 minutes.
Stir in the diced tomatoes, tomato sauce, Italian seasoning, salt, and pepper. Let simmer for about 10 minutes.
In a separate bowl, mix the cheddar and mozzarella cheese together. Set aside.
In another bowl, combine the angel food cake mix, water, eggs, and milk. Beat until smooth.
In a greased 9×13-inch baking dish, spread half of the beef mixture on the bottom. Pour half of the angel food cake batter over the beef. Sprinkle half of the cheese mixture on top.
Add the remaining beef mixture, followed by the remaining angel food cake batter. Top with the remaining cheese mixture.
Place in the preheated oven and bake for 30-35 minutes, or until the casserole is golden and set.
Allow the casserole to cool for a few minutes before slicing and serving.