Heat the oven to 400 F. Lightly oil a shallow, 9×13-inch baking dish. Pat the fish dry and add it, skin side down, to the pan. Brush each fillet lightly with olive oil, and sprinkle with salt and pepper. Pour the wine in the pan, scatter the grapes around, and sprinkle the pistachios and parsley on top of the fish.

Roast the salmon for 7 minutes for medium-rare; 8 minutes for medium.

While the fish cooks, in a large bowl, toss the spinach, onion, oil, and vinegar. Season with salt and pepper, toss again, and divide among 4 plates.

Place the fish on top of the greens. Spoon the roasted grapes around the fish.