1.
To prepare the remoulade, combine all the ingredients except the orange zest in a blender or food processor, processing until smooth. Refrigerate for 20 to 30 minutes, covered, until ready to serve. Present in a bowl, garnished with orange zest. This makes a great condiment to use on rice, too.
2.
To prepare the fish, combine the thyme, cayenne, paprika, salt, garlic powder, and white pepper in a small bowl. Mix and set aside.
3.
Wipe the grouper fillets clean, then coat both sides of the fillets with half the butter. Pat both sides thoroughly with the spice rub.
4.
Heat a large cast-iron skillet until it is smoking hot. Add some of the remaining butter, decrease the heat to medium-high, and add the grouper fillets.
5.
Cook until nicely browned, about 3 minutes, then turn to cook the other side, adding the rest of the butter to the skillet. Cook until browned on the second side, about 2 minutes longer.
6.
Serve hot with the remoulade sauce.