Preheat oven to 350ºF. Prepare two standard muffin pans by lining 16 of the cups with paper liners.
Whisk together eggs, milk, salt and pepper; stir in sausage, cheese and tomato. Divide mixture among muffin cups (about 1/3 cup of egg mixture per quiche). Bake for 20-25 minutes, until the filling is set. Cool in muffin pan for 5 minutes, then transfer quiches to a wire rack to cool completely.
If desired, you can return the cooled quiches to the muffin pans and transfer to freezer, then pack into freezer bags once frozen.
Notes
Sausage substitute: You may substitute turkey or chicken sausage, cubed ham, small pieces of cooked chicken, or a cooked vegetable like zucchini or small cubes of butternut squash.