Combine the turkey, spinach, feta, red onion, Greek seasoning mix, garlic, and egg in a large mixing bowl. Make sure it is well combined, using your hands if necessary. (Be sure to wash your hands afterwards).
Form four even patties with the mixture and set aside.
Preheat your grill, grill pan, or indoor grill to medium heat (for grilling outdoors, I suggest having your grill around 350°F- 400°F).
If using a grill pan or indoor grill, I suggest spraying it with nonstick spray. Lean turkey doesn’t have a lot of fat, so it may stick a little without it. You can rub olive oil on the outdoor grill grates.
Add your patties to the grill and grill about 4-5 minutes per side. Making sure they are cooked through. Remove from the grill and set aside to rest.
Once removed, make your tzatziki sauce. Start by adding your cucumber and ½ teaspoon kosher salt to a bowl and mix around. Let it sit for 10 minutes to extract extra water from the cucumbers.
Remove the cucumbers from the bowl and squeeze with cheesecloth or a paper towel to remove the water and return them back to the bowl.
Add in your garlic, lemon zest, lemon juice, fresh dill, salt, and pepper. Mix together.
Drizzle in the olive oil and mix to combine.
Add your turkey burger to your bun, top with tzatziki sauce (additional red onions if desired), and lettuce. Serve it up and enjoy!
Notes
I suggest spraying your grill (indoor, pan, or outdoor) with nonstick spray or olive oil. Turkey is lean and will sometimes stick.
If your turkey burgers are falling apart, your ground turkey may have had added water. You can add a little breadcrumbs to the mix to help them hold together better.
Having an even, uniform patty really helps with making sure it cooks properly and evenly. I like using this patty maker to make sure they are all the same size.
To ensure that your burgers aren't over cooked or under cooked, I highly recommend using an instant read meat thermometer.
Salting the cucumbers and draining them is not a required step, but I highly recommend it. It will keep your tzatziki from becoming watery.
Fresh dill really makes a difference in the tzatziki sauce so if you can find it, definitely use it!
Nutrition information is based on the exact products I used and does not include the hamburger bun.