Preparation

• Soak the cedar planks in water to cover for at least 1 hour. Drain the planks.

Prepare the sauce

• In a small bowl, stir the crème fraîche, chives, and horseradish. Season to taste with salt and pepper. Refrigerate.

Prepare the salmon

• In a small bowl, combine the lemon zest, thyme, sugar, 1 1/2 tsp. salt, and 1 Tbs. pepper. Rub the mixture together with your fingers until the zest is distributed throughout. Rub the salmon fillets on both sides with the olive oil and then set each fillet skin side down on a plank. Sprinkle the fillets with the lemon-pepper mixture, dividing it evenly. Gently rub the seasoning into the fillets. Let stand at room temperature while the grill heats.

Cook the salmon

• Prepare a gas or charcoal grill fire for indirect cooking with high heat: On a gas grill, heat all burners on high; then turn off all but one burner just before cooking the salmon; on a charcoal grill, bank the coals to two opposite sides of the grill. Arrange the planks over the cooler part of the grill, positioning them so that the thickest part of the fish is closest to the heat source. Cover the grill and cook until the thickest part of each fillet registers about 135°F on an instant-read thermometer, 20 to 35 minutes depending on the thickness of the fillets. The planks may smoke a bit (this is fine) and will become very aromatic. Let the fillets rest on the planks for 5 to 10 minutes before serving.Cut the salmon fillets crosswise into serving portions and transfer to individual plates. Serve with the sauce.

Make Ahead Tips

The sauce may be made up to 1 day ahead, and refrigerated, covered.

To round out your Sunday supper, serve this dish with Peas and Carrots with Lemon, Dill, and Mint.

Cool any leftover salmon completely, wrap well, and refrigerate for up to 3 days.