Place tomatoes in a pan of boiling water for 1 to 2 minutes or until skins easily slip off. Drain and rinse with cold water. Peel; thinly slice. Place in a bowl with onion.
In a small bowl, mix remaining ingredients. Pour over tomatoes and onions. Let stand at room temperature for about 15 minutes. Serve with hot, crisp Italian bread or to accompany roast beef or baked chicken.
Yield: Four to six servings.