Savory Sunday: Spanakopita Turkey Burgers

Name: Savory Sunday: Spanakopita Turkey Burgers
Ingredients: 1/2 large red onion, diced; 2 cloves garlic, minced; 1 tablespoon olive oil; 1 1/4lbs ground turkey (we like 93/7); 1/2 cup feta cheese, crumbled; 10 ounces frozen spinach, thawed and drained (see note); 2 tablespoons kalamata olives, chopped; 1 tablespoon fresh oregano, chopped (can substitue 1 teaspoon dried oregano); 1 1/2 teaspoons Montreal Steak Seasoning; Optional toppings: thinly sliced red onion, tomato, arugula or lettuce; 5-6 burger buns (we enjoyed our burgers with some homemade sourdough whole wheat buns)