Preheat oven to 425°F.
Mix yogurt, a grated clove of garlic, cucumber, the juice of 1 lemon and ½ teaspoon cumin. Set aside, chill in refrigerator.
Slice the tomatoes and remaining cucumber.
Defrost spinach in microwave and squeeze out the moisture. NOTE: I use my potato ricer to squeeze out the water.
Place the ground lamb (or combination of lamb and beef) in a bowl. Add grill seasoning, 2 teaspoons cumin, chili powder, coriander, oregano, cinnamon and feta crumbles. Add the spinach. Mix up the lamb, seasonings and spinach, and form a long 3-inch roll on a baking sheet. Coat lamb with extra-virgin olive oil and bake 20 minutes.
Soften pita over open gas flame or under broiler.
Slice lamb loaf into ¼-inch slices. Spread tzatziki sauce on pitas and top with a 2 slices of lamb, tomatoes, cucumbers and any other garnishes (such as sprouts or lettuce) as you desire.
