1/2 red onion, very thinly sliced (about 2 ounces)
1 garlic clove, minced
1/4 cup red wine vinegar
1/3 cup extra-virgin olive oil
Kosher salt
Freshly ground pepper
1 red bell pepper, cut into 1-inch pieces
1/3 English cucumber, thinly sliced (1/4 pound)
1/4 cup torn basil leaves
1/4 cup coarsely chopped mint
1/4 cup coarsely chopped fresh dill
1 pound assorted heirloom tomatoes, cut into bite-size pieces
4 ounces feta cheese, crumbled
In a small bowl, cover the onion slices with ice water and let stand for 10 minutes. Drain the onion.
In a large bowl, combine the garlic and vinegar. Whisking constantly, drizzle in the olive oil. Season with salt and pepper. Add the bell pepper, cucumber, basil, mint, dill, and onion, and toss to coat. Let marinate for 15 minutes, stirring occasionally. Add the tomatoes and toss gently; season with salt and pepper. Transfer the salad to a platter, top with the feta and serve.