1/4 cup red wine vinegar
1/2 tsp kosher salt
1/4-1/2 tsp freshly ground black pepper
1/2 cup extra virgin olive oil
1-2 small cucumbers, peeled
1/2 small red onion
3 heirloom tomatoes (about 12 oz total), cut into bite-sized chunks
3 1/2 cups watermelon, peeled, seeded, and cut into bite-sized chunks
1 red bell pepper, cored, seeded, and cut into bite-sized chunks
7 oz feta cheese, cut into 1/2 inch cubes
fresh mint leaves thin sliced
Whisk vinegar, salt and pepper in a medium bowl to blend. Gradually whisk in the oil to blend well. Set aside.
Cut the cucumber in half lengthwise, then, using a spoon, scrape out the seeds. Cut the cucumber halves crosswise into thin half-moon slices. Using a mandoline or sharp knife, cut the onion into 1 inch long paper thin slices. Toss the sliced cucumber, onion, tomatoes, watermelon, bell pepper, cheese and mint in a large bowl with enough vinaigrette to coat. Serve immediately. Refrigerate leftovers.