- 1/2 cup (1 stick) butter, room temperature
- 3 tablespoons frozen orange juice concentrate, thawed
- 1/2 teaspoon Champagne vinegar or white wine vinegar
- Large pinch of saffron threads
- Coarse kosher salt or coarse sea salt
- 6 whole farm-raised striped bass or trout (about 1 pound each), gutted, cleaned, top fin cut off
- 2 large oranges; 1 juiced, 1 halved, then thinly sliced
- Nonstick vegetable oil spray
- Whisk butter, juice concentrate, vinegar, and saffron in small saucepan to blend. Season butter to taste with coarse salt and pepper. DO AHEAD Can be made 2 days ahead. Cover and chill.
- Using small sharp knife, cut diagonal slits on both sides of fish at 1-inch intervals. Arrange fish on rimmed baking sheet. Sprinkle fresh orange juice and salt into slits and cavities of fish. Fill cavities with orange slices (about 3 per fish). Cover loosely and let stand at room temperature at least 30 minutes and up to 1 hour.
- Spray grill racks and fish generously with nonstick spray. Prepare barbecue (medium-high heat). Place saucepan with orange-saffron butter at edge of grill to warm through, stirring occasionally. Arrange fish on barbecue. Grill until just opaque in center, about 5 minutes per side. Transfer to plates. Serve with warm seasoned butter.