We love tomatoes & cucumbers. Here is a recipe that works great for both. Unfortunately I don't have measurements but we just go by the taste. Slice & lay out on a dish. Dice a vidalia onion & sprinkle liberally. Start with a 1/2 cup of oil, (we use canola) & start adding red wine vinegar. I would suggest 2 tablespoons to start. Depending on your tastes, you can keep adding the vinegar. We also add just a little bit of sugar to this mixture. Drizzle over tomatoes/cucumbers. You want to cover them in the oil mixture. We then sprinkle parsley or basil over top & refrigerate for about 15 min.
Hope this helps you out!
Sue