In a large, resealable bag, combine the onion, oil, vinegar, basil, parsley, garlic, sugar, salt, and pepper.
Gently add the tomatoes and coat them with the marinade. Refrigerate for at least an hour, turning the bag once. When ready to eat, serve over a bed of spinach leaves. Enjoy!
Recipe by Epicurean Vegan at http://epicureanvegan.com/2015/09/09/marinated-tomato-salad/