I don't, but it sounds delicious! Could this be it? This one doesn't mention onion though.
http://www.nytimes.com/2008/07/21/he...cipe.html?_r=1
Summer Salad with Feta
5 medium or large ripe tomatoes cut into wedges (if large, the wedges should be cut crosswise in half), or 1 pint of cherry tomatoes cut in half
1/2 European cucumber, or 1 Persian or Japanese cucumber, cut in half lengthwise, seeded if desired, then sliced into half circles about 1/3-inch thick.
Sea salt or fleur de sel and freshly ground pepper
2 tablespoons red wine vinegar or sherry vinegar
1/4 cup extra virgin olive oil
1/2 cup crumbled feta
1 to 2 tablespoons chopped fresh mint, or 3/4 teaspoon dried oregano
Toss together the tomatoes, cucumber, salt, pepper, vinegar, and olive oil. Add the feta and herbs, and toss again. Taste, adjust the seasonings, and serve.
Then I found this one:
Cherry Tomato Cucumber Feta Salad Recipe
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Ingredients
2-3 cups of cherry and/or pear tomatoes, sliced in half
1 cup of chopped cucumber, peeled (and seeded if the seeds are bitter)
1/4 cup crumbled feta cheese
1 Tbsp chiffonaded mint leaves
1 teaspoon fresh, chopped oregano
1 Tbsp lemon juice
2 Tbsp of finely chopped shallots or green onions
2 teaspoons olive oil
Coarse salt and freshly ground black pepper to taste
Method
Gently toss the tomatoes, cucumber, feta, onions, mint, and oregano together. Dress with lemon juice, olive oil, salt and pepper to taste.
Serves 2-4.
Cherry Tomato Cucumber Feta Salad Recipe | Simply Recipes
I'm sure she'd be happy to give you her recipe. I'm always flattered if someone asks me for a recipe!