Combine sour cream, 2 tablespoons dill, 2 tablespoons vinegar, shallots, rind, juice, and garlic in a bowl, stirring well; cover and chill.
Sprinkle fish evenly with salt and freshly ground black pepper. Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add fish to pan, and cook for 3 minutes. Turn fish over, and cook 1 minute. Remove from heat. Add wine; cover and let stand 3 minutes or until fish flakes easily when tested with a fork or until desired degree of doneness.
Using a vegetable peeler, shave cucumber lengthwise into ribbons to yield about 2 cups. Combine cucumber, remaining 1 tablespoon rice vinegar, and remaining 1 teaspoon dill in a bowl; toss gently to coat. Place about 1/2 cup cucumber mixture on each of 4 plates; top each serving with 1 fillet and 2 tablespoons sour cream mixture.
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