Preheat a cast iron skillet over medium heat.
In the meantime, in a large bowl, mix together ground turkey, spinach, garlic, salt, ground black pepper, cumin and 2 tbsp of the oil. Mix until thoroughly combined. Portion into 8-10 burgers. Lightly flatten then and place your thumb in the middle of each one so it has a slight indent. This will help the burgers cook flat and not round too much at the top.
Add the remaining 1 tablespoon of oil in the cast iron skillet. Place 4-5 burgers on the skillet and cook for 3-4 minutes on each side until browned and the turkey is no longer pink and cooked through, and the temperature reads 165F. Repeat with remaining burgers.
Serve with toppings such as lettuce, tomato, salsa, avocado, grilled onions, and mustard.