Prepare the tzatziki. Cut the cucumber in half and scrape out the seeds using a spoon. Grate the cucumber, season with ¼ teaspoon salt, and let sit for 10 minutes in a colander. Squeeze out excess moisture. Combine the cucumber with yogurt, garlic, lemon juice, and dill. Season with salt and pepper. Let sit for 30 minutes.

Prepare the burgers. Mix together ground turkey, garlic, salt, pepper, sun dried tomatoes, feta, and chopped spinach. Shape into 4 patties. Cook on the grill, stove top, or in the oven until the juices run clear.

Assemble burgers with spinach, sliced tomatoes, and tzatziki. Serve.