If you're serving a bunch, this dish can easily be doubled.
Place tomatoes and onion in a serving dish. Set aside.
Bring vinegar and next 7 ingredients to a boil in a saucepan over medium-high heat. Boil 1 minute.
Pour vinegar mixture over tomato mixture. Cover and chill at least 1 hour.
Note: Salad may be prepared in advance and chilled up to 3 days.
