Grate zest from 1 grapefruit to make 1/2 teaspoon; set aside. Peel and section grapefruit, and set aside. Juice remaining grapefruit to make 1/4 cup juice; set aside.
Heat oil and 1 tablespoon butter in a large skillet over medium heat. Sprinkle fillets with salt and pepper. Cook in batches, adding more oil if necessary, 2 minutes on each side or until done. Transfer to a plate, cover, and keep warm.
Combine reserved grapefruit juice, wine, and next 3 ingredients. Bring to a boil over high heat, and cook until reduced to about 1/4 cup. Remove from heat; whisk in 6 tablespoons butter. Stir in reserved grapefruit sections and zest. Season to taste with salt and pepper. Serve fillets topped with Grapefruit-Thyme Butter.
Wine pairing: A Fumé Blanc, Sauvignon Blanc, or crisp Chardonnay will complement any citrus-seafood dishes (perhaps served with a tossed green salad and crusty French bread) for a light, refreshing supper.