Greek Style Grass-fed Beef Burger with Zaziki

1 lb grass-fed beef hamburger
1 small onion, minced
1 clove of garlic
3 oz Feta cheese, diced or crumbled
4 TB cooked spinach
1 egg
salt, pepper, 1/2 ts cumin
Mix hamburger with onion, crushed garlic, egg, spices, spinach and feta cheese. Add seasoning and form hamburger patties as you like them.
Fry in cast-iron pan until brown on both sides. Don't overcook these burgers - they should be at least medium! Serve with Zaziki and tomatoes, lettuce and your favorite hamburger buns.