Grilled Fish with Citrus Pearl Sauce

Using a sharp knife, peel 1 of the oranges, removing all of the bitter white pith, then cut in between the membranes to release the sections. Using a fork, gently break up the sections into pearls; you will need 2 tablespoons. Repeat with 2 sections of the grapefruit to yield 2 tablespoons of pearls, and with the lime to yield 1 tablespoon of pearls. Juice the remaining orange and grapefruit to yield 1/2 cup each of juice.

In a small skillet, simmer the orange and grapefruit juices over moderately high heat until reduced by half, about 10 minutes.

Light a grill. Brush the fish with olive oil and season with salt and pepper. Grill over a hot fire until just cooked through, 3 minutes per side for pompano or mackerel, 5 minutes for halibut. Transfer to plates.

Bring the reduced juice to a boil and add the citrus pearls. Remove from the heat and whisk in the 1 tablespoon of olive oil, then the butter. Season with salt. Spoon over the fish and serve.