Prepare the Meat Mixture:In a large bowl, combine the ground beef, chopped onion, tomato paste, sumac, chili powder, paprika, allspice, cumin, cinnamon, salt, and pepper. Mix well until all ingredients are evenly incorporated.
Cook the Meat: Heat a cast iron pan over medium-high heat. Take a small ball of the meat mixture and place it on the tortilla. Use a spatula to smash the meat flat onto the tortilla. Place the tortilla with the meat side down onto the hot pan.
Cook the Tacos: Cook for about 3-4 minutes until the meat is browned and crispy, then flip and cook the tortilla side for an additional 1-2 minutes until crispy. Remove from the pan and keep warm. Repeat with the remaining meat mixture and tortillas.
Prepare the Sauce: In a small bowl, mix the Greek yogurt, parsley or cilantro, mint, lemon juice, grated garlic, and salt. Adjust the consistency with water if needed.
Assemble and Serve: Serve the tacos with chopped tomatoes and sumac onions on the side. Spread a generous amount of the yogurt sauce on each taco. Garnish with optional chopped parsley.