In a small bowl, whisk together lemon zest, lemon juice, olive oil, and garlic. Stir in 2 tablespoons fresh basil and capers. Season vinaigrette to taste with salt and pepper. NOTE: Can be prepared 1 hour ahead. Let stand at room temperature until ready to use.
Prepare barbecue (medium-high heat) or preheat broiler. Season halibut steaks with salt and pepper. Brush halibut with lemon vinaigrette, dividing equally.
Grill or broil halibut steaks approximately 4 minutes per side or until a meat thermometer registers an internal temperature of 140 degrees F (halibut will be slightly opaque in thickest part). Remember the halibut continues to cook after it is removed from the heat source.
Approximately cooking times for halibut:
1/4 to 1/3-inch - 3 to 4 minutes
1/2 to 3/4-inch - 4 to 6 minutes
1 to 1 1/2-inch - 8 to 12 minutes
This is the type of cooking and meat thermometer that I prefer and use in my cooking. I get many readers asking what cooking/meat thermometer that I prefer and use in my cooking and baking. I, personally, use the Thermapen Thermometer shown in the photo on the right. To learn more about this excellent thermometer and to also purchase one (if you desire), just click on the underlined: Thermapen Thermometer.
Carefully transfer fish to individual serving plates. Whisk remaining lemon vinaigrette; pour over fish. Garnish cooked halibut with remaining 1 tablespoon basil leaves and serve.
Makes 4 servings.