Dry the green onions and garlic: Heat a pan over very low heat and brush with a tiny bit of oil. Add the chopped green onions and garlic cloves. Dry them out gently for about 1 minute without browning or cooking.
Combine ingredients: Remove the pan from heat. Mix the dried green onions and garlic with sesame seeds, zaatar, salt, black pepper, cumin, coriander, turmeric, cardamom pods, cinnamon, and dried chili peppers in a bowl.
Grind the spice mixture: Grind the mixture finely using a blender, spice mixer, or coffee grinder. Because of moisture from onions and garlic, the mixture may become clumpy.
Dry the spice mixture in the oven: Spread the ground mixture on a non-stick baking pan and place in a preheated oven at 250°F (about 120°C). Heat for about 15 minutes at a time, breaking up clumps with a fork, until all moisture evaporates, approximately 30 minutes total.
Adjust seasoning and final grind: Optionally add more dried chilies and turmeric for extra spiciness and color. Grind the mixture one final time to achieve a fine texture.
Serve and store: Serve the spice mixture as a condiment with boiled potatoes, yogurt, eggs, bread, or other dishes. Store in airtight bags or containers for several months.