To prepare sauce, blend tomatoes and their liquid with onion and garlic in a food processor or blender. Pour into a medium sized saucepan. Add red pepper, salt and tomato paste. Heat to a boil; then simmer for 5-10 minutes.
Place 3 tortillas in bottom of Crock Pot. Layer on tortillas in this order: 1/3 of the ground beef, 1/3 of the tomato sauce and 1/3 of the Cheddar cheese. Repeat each layer two more times.