On broiler pan or in microwave-safe dish, arrange fillets in single layer with thickest part to outside.
Brush with lemon juice; sprinkle with garlic and dill.
Broil for 6 to 8 minutes or microwave, covered loosely with waxed paper, at high (100%) power for 4 to 5 minutes or until fish is opaque and flakes easily when tested with fork.
Cucumber-Yogurt Sauce: Meanwhile, in small dish, combine yogurt, sour cream, cucumber, onion, and pepper to taste; mix well.
Spread over fish and broil for 2 minutes or micro wave at high (100%) power for 1 minute or until sauce is hot.