Mix the cumin, coriander, paprika, turmeric, cloves, cayenne pepper and cinnamon in a small bowl.
Slice the flank steak into thin, bite sized pieces. Pro tip: this works best when the meat is still partially frozen. Aim for about 1/4 inch thick slices.
Place steak in a large bowl, and season with salt and pepper. Add olive oil, white wine vinegar, lemon juice and zest, minced garlic and sliced onions. Toss ingredients well to combine and add the shawarma spices. Work the marinade into the meat with your hands.
Let the meat marinate at room temperature for about 30 minutes. Or, keep it in the fridge for a few hours or up to overnight.