01 - In a large bowl, combine the ground beef, red onion, garlic, breadcrumbs, egg, parsley, mint, oregano, cumin, lemon zest, salt, and pepper. Mix gently until just combined, being careful not to overwork the mixture.
02 - With wet hands to prevent sticking, form the mixture into walnut-sized balls, yielding approximately 20 meatballs.
03 - Heat olive oil in a large nonstick skillet over medium heat. Fry the meatballs in batches, turning occasionally, until evenly browned and cooked through, about 8 to 10 minutes. Transfer to a plate lined with paper towels to drain.
04 - While the meatballs cook, combine the Greek yogurt, lemon juice, fresh dill, garlic, salt, and pepper in a small bowl. Stir until smooth and adjust seasoning to taste.
05 - Arrange the hot meatballs on a serving platter with the yogurt sauce on the side. Garnish with additional fresh parsley if desired.