We like ground turkey or chicken for its low fat content and finer texture, but you can sub in ground pork, beef, or lamb for heartier meatballs. Golden raisins give it a hint of sweetness. If you prefer, use another dried fruit, such as chopped dried apricots or apples.
Preheat oven to 450°F. Line a large rimmed baking sheet with parchment paper. Remove zest from lemon; add to a medium bowl. Stir in the panko, half of the green onion, the walnuts, raisins, egg, the 2 Tbsp. chopped mint, the cumin, garlic, crushed red pepper, salt, and black pepper until well-combined. Add turkey, and mix just until combined.
Form meat mixture into 1½-inch meatballs and arrange on prepared baking sheet. Bake, turning once, until meatballs are cooked through(160°F) and lightly browned, 15 to 20 minutes.
Meanwhile, for sauce, squeeze the juice from the lemon into a small bowl. Stir in yogurt, olive oil, and the 2 tsp. mint. Season to taste with salt and black pepper.
Serve meatballs with sauce over couscous, farro, or rice. Top with remaining chopped green onions.