Start with bell peppers to make a super easy version of that classic Italian casserole

1 cup uncooked rice
2 cups water
3 large bell peppers (any color), diced
1 tablespoon olive oil
1 onion, chopped
2 cloves garlic, minced
1 pound ground beef
1 teaspoon salt
1/2 teaspoon black pepper
1 can (14.5 oz) diced tomatoes, undrained
1 teaspoon Italian seasoning
2 cups shredded cheddar cheese
1/2 cup mozzarella cheese, for topping