*** In frying pan, saute onions in butter until tender. Do not brown. Stir in tomatoes, chili peppers and salt. Simmer for 15 minutes. Cube cheddar cheese. Add cheese a few pieces at a time into frying pan. Stir until all the cheese is melted. Pour into chafing dish or fondue pot. Keep warm. Serve with corn chips. Thin mixture with milk if thick.