Stuffed Pepper Soup

Name: Stuffed Pepper Soup
Ingredients: 1 medium red bell pepper; 1 medium green bell pepper; 1 medium orange bell pepper; 1 small yellow onion; 2 cloves garlic; 2 tablespoons olive oil; 1 pound lean ground beef; 1 teaspoon kosher salt; 1/2 teaspoon ground black pepper; 6 cups low-sodium beef broth, plus more as needed; 2 (14.5-ounce) cans petite diced tomatoes; 1 (15-ounce) can tomato sauce; 2 teaspoons Italian seasoning; 1/4 teaspoon red pepper flakes (optional); 1 cup uncooked long-grain white rice; 4 ounces sharp cheddar cheese; 1/2 bunch fresh parsley