In a bowl, mix together the turkey, spinach, chopped olives and feta, cumin, garlic powder, salt and pepper.
Form the mixture into 4 burger patties.
Carefully press a shallow indentation into the center of each of the burger patties.
Grease a baking tray with olive oil and place the burger patties on the tray.
Cook for 10 minutes in the oven, then flip them over and cook for another 8 to 10 minutes on the other side.
When the turkey burgers are cooked, remove them from the oven and assemble the burger.
Slice a burger bun in half and add a spoonful of tzatziki, 3 slices of cucumber, a few onion slices, and a small handful of salad leaves. Top with a turkey burger patty.