Heat the butter in a 3-quart saucepan over medium-high heat. Add the onion and pepper and cook for 5 minutes or until the vegetables are tender, stirring occasionally.
Add the tomato and garlic to the saucepan and cook and stir for 1 minute. Season with the salt and black pepper.
Stir in the soup and milk and heat to a boil. Remove the saucepan from the heat. Add the cheese and stir until melted. Stir in the macaroni. Sprinkle with the cilantro.
