Start to finish: 45 minutes
Hands on time: 20 minutes
Servings: 4

2 tablespoons extra-virgin olive oil, divided
1/2 cup finely chopped onion
5 ounces baby spinach
Kosher salt and ground black pepper
1/4 cup plain nonfat Greek yogurt
1/4 cup low-fat mayonnaise
2 tablespoons minced seeded pepperoncini
1 tablespoon liquid from the pepperoncini jar
1 to 2 teaspoons lemon juice, or to taste
1 teaspoon minced garlic
3 ounces crumbled feta cheese
2 tablespoons chopped fresh oregano
1 pound ground turkey (for grinding your own meat, see page 000)
¼ teaspoon kosher salt
¼ teaspoon freshly ground black pepper
4 whole-wheat hamburger buns, toasted

Heat the grill to medium.

Heat 1 tablespoon of the oil in a large skillet over medium heat. Reduce the heat to medium low, add the onion and cook, stirring occasionally, until golden brown, about 10 minutes. Increase the heat to medium high, add the remaining tablespoon of olive oil and the spinach and cook, stirring, until the spinach is wilted. Season with salt and pepper and transfer the mixture to a bowl. Chill in the refrigerator until cooled to room temperature.

Meanwhile, combine the yogurt, mayonnaise, pepperoncini, pepperoncini liquid, lemon juice, garlic, and salt and pepper to taste in a small bowl and set aside.

Once the spinach has cooled, remove it from the refrigerator and add the feta, oregano, ground turkey, 1/4 teaspoon salt and 1/4 teaspoon pepper. Mix well and shape into 4 patties, each about 1/2-inch thick.

Spray the burgers lightly with olive oil cooking spray, then grill over medium heat until just cooked through, about 6 minutes per side.

Spread some of the yogurt sauce on the bottom half of each bun, then top with a burger. Spoon the remaining sauce over the burgers and top with the remaining bun halves. Serve immediately.