Directions

1. 1

   Prepare the vinaigrette by whisking together the red wine vinegar, olive oil, kosher salt, and black pepper in a small bowl until well combined. If making ahead, transfer to a tightly sealed jar and refrigerate up to 1 week. Before using, let the vinaigrette sit at room temperature for about 20 minutes to allow the oil to fully liquefy, then shake well to emulsify.

2. 2

   Prepare the cucumber by cutting it in half lengthwise. Using a spoon, carefully scrape out and discard the seeds from each half. Then cut the halves crosswise into thin half-moon slices and set aside.

3. 3

   Slice the red onion paper-thin using a mandoline or sharp knife into 1-inch-long pieces.

4. 4

   Cut the heirloom tomatoes into bite-size chunks, being careful not to cut them too far in advance to prevent oxidation and browning.

5. 5

   Cut the red bell pepper into bite-size chunks of similar size to the other vegetables.

6. 6

   In a large serving bowl, gently combine the sliced cucumber, thin onion slices, tomato chunks, watermelon chunks, bell pepper chunks, feta cheese cubes, and fresh mint.

7. 7

   Pour enough of the red wine vinaigrette over the salad to lightly coat all ingredients, then toss gently to combine, being careful not to break up the cheese or watermelon pieces. Serve immediately while all ingredients are fresh and cool.