Red Wine and Feta Vinaigrette

Preheat a grill pan. Brush onion slices with olive oil and season with salt and pepper. Place onions on grill pan and cook, turning, until tender, 4 to 5 minutes. Transfer to a small bowl; drizzle with olive oil and lemon juice. Toss to combine.

Transfer onion to the bowl of a food processor along with vinegar, basil, thyme, feta, mustard, garlic, shallots, oregano, 1 tablespoon salt, and 1 tablespoon pepper; pulse to combine.

With the processor running, slowly drizzle in 3/4 cup olive oil until dressing is smooth; season with salt and pepper.