Preheat the oven to 400 degrees F.
Cut the bell peppers in half top to bottom and remove the seeds and ribs. Set aside. Cook the rice in a medium saucepan following the package directions.
In a medium skillet, brown the ground beef with the onion and garlic over medium-high heat, 6 to 8 minutes. Drain any excess fat from the meat and remove the skillet from the heat. Combine the ground beef mixture, rice, tomatoes, black pepper and salt in a large bowl and mix until blended.
In a 9-by-13-by-2-inch baking dish, place the bell peppers cut-side up. Evenly divide the beef mixture among the pepper halves. Cover the dish with foil and bake for 20 minutes. Remove the foil and sprinkle the Cheddar on top. Return the pan to the oven, uncovered, and bake until the cheese melts, about 5 minutes.
Adapted from "Home Cooking with Trisha Yearwood" by Trisha Yearwood. Copyright Clarkson Potter 2010. Provided courtesy of Trisha Yearwood. All rights reserved.