Rinse 1 cup tiny cherry tomatoes (about 3/4 in. wide; red, yellow, orange, or a mixture). Cut tomatoes into halves and put in a bowl. Add 1 tablespoon minced mild onion, 1 tablespoon minced fresh tarragon leaves, 2 teaspoons olive oil, and 1 teaspoon white wine vinegar. Stir to mix; add salt to taste.
If making sauce up to 1 day ahead, cover and chill.
Nutritional analysis per tablespoon.