Prepare the Burgers : In a large mixing bowl, combine the ground turkey, chopped spinach, crumbled feta, grated onion, whisked egg, minced garlic, dried basil, salt, and pepper. Mix thoroughly until all ingredients are well incorporated. Shape the mixture into burger patties of your desired size. Aim for about 4-5 patties for even cooking.
Cook the Burgers : Heat a non-stick skillet or grill over medium heat. Lightly grease with olive oil. Cook the burgers for 5-6 minutes on each side, or until the internal temperature reaches 165°F (75°C).
Make the Tzatziki Sauce : While the burgers cook, prepare the tzatziki sauce. Start by squeezing the grated cucumber with a clean kitchen towel to remove excess moisture. In a bowl, mix the drained cucumber with Greek yogurt, lemon juice, olive oil, minced garlic, sea salt, and chopped dill. Stir well to combine.
Assemble and Serve : Serve the turkey spinach burgers on a plate or in a whole-grain bun. Add a dollop of tzatziki sauce on top and garnish with extra dill or fresh spinach leaves if desired. Enjoy warm with a side of roasted vegetables, salad, or sweet potato fries.