Rinse fish; pat dry. Season fish with salt and pepper. In bowl combine Dijon-style mustard, 2 tablespoons dill, and 1 tablespoon olive oil. Spread mustard mixture over both sides of fish.
In a bowl combine tomatoes, garlic, and remaining dill and olive oil; season to taste with salt and pepper.
Heat a cast iron or nonstick skillet over medium-high heat. Add fish to skillet. Cook 8 to 10 minutes or until fish flakes easily, turning once. Transfer to serving plate. Add tomato mixture to skillet. Cook and stir 1 minute. Serve tomato mixture with fish. Makes 4 servings.