To keep these patties strictly keto, use full-fat feta cheese and a keto-friendly tzatziki made with unsweetened Greek yogurt or sour cream, olive oil, cucumber, garlic, lemon, and herbs. If your ground turkey is very lean, avoid overcooking so the patties stay moist, and feel free to add another tablespoon of olive oil to the mixture for extra richness. You can swap spinach for finely chopped kale or chard, making sure to remove tough stems and chop the leaves very finely. For baking instead of pan-searing, arrange patties on a parchment-lined baking sheet, brush lightly with olive oil, and bake at 400°F for about 15 to 18 minutes, broiling briefly at the end for browning. Always check that the internal temperature reaches 165°F for food safety.