Stir together 1/2 cup plain yogurt, juice of 1 lemon, 1 tbsp extra-virgin olive oil, 2 to 3 cloves garlic, smashed, 1 1/2 tsp ground coriander, 1 1/2 tsp ground cumin, 1/4 tsp salt, and pepper to taste in a small bowl. Pour half of the sauce into a large resealable plastic bag; cover and refrigerate the remaining sauce. Add 4-6 -ounce skinless center-cut salmon fillets to the bag and turn to coat with the marinade. Refrigerate for 20 to 30 minutes, turning the bag over once. Preheat a grill to medium-high. Remove the salmon from the marinade and blot off excess yogurt with paper towels. Lightly oil the grill and add the salmon; cook, turning once, until browned on the outside and opaque in the center, 4 to 6 minutes per side, depending on the thickness. Serve with the reserved yogurt sauce and garnish with 1/4 cup chopped fresh cilantro or parsley and lemon wedges.