In a pan over low heat, add butter. When it begins to melt, add onions and cook for about 1 to 2 minutes or until limp. Add tomatoes and cook, mashing with back of spoon, until softened. Season with salt and pepper to taste.
Pour eggs over tomato-onion mixture and allow to cook without stirring for about 20 to 30 seconds. When it begins to set, gently fold with tomatoes and onions until combined. Continue to cook until eggs are just set. Serve hot.