01 - In a large bowl, combine the ground beef, red onion, garlic, breadcrumbs, egg, parsley, mint, oregano, cumin, lemon zest, salt, and pepper. Mix 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 golden brown and cooked through, about 8 to 10 minutes. Drain on paper towels.
04 - While the meatballs cook, combine the Greek yogurt, lemon juice, fresh dill, and minced garlic in a small bowl. Season with salt and pepper to taste and stir until smooth.
05 - Arrange the hot meatballs on a serving platter with the yogurt sauce on the side. Garnish with extra fresh parsley if desired.