Spinach Feta Turkey Burgers with Tzatziki

• 1 lbground turkey
• 1egg — whisked
• 1 cupspinach — finely chopped
• ½ cupfeta cheese — finely crumbled
• ¼ cupplain breadcrumbs
• 3garlic — finely minced or microplaned
• 1 tsponion powder
• ½ tspsalt
• ¼ tspfreshly ground black pepper
• —For serving: Buns, thinly sliced red onion, tomato, lettuce, extra feta, Greek yogurt tzatziki sauce

Greek yogurt tzatziki

• 1 cupplain Greek yogurt
• ½ cupcucumber — diced very small
• 2 tbspfresh dill — finely chopped
• 1garlic — finely minced or microplaned
• 1–2 tspfreshly squeezed lemon juice
• ¼ tspsalt
• ¼ tspfreshly ground black pepper