Season both sides of grouper fish fillets liberally with the salt, black pepper, and cayenne pepper.
Heat an enameled cast iron skillet over medium-high heat.
When heated, melt the 2 tablespoons of butter in the skillet.
When melted, add the grouper fillets.
Sear for 2 minutes on each side, then transfer to a plate.
Lower heat to medium.
Use a wooden cooking spoon to pick up any overly charred bits from the bottom of the skillet.
Add the cold stick of butter.
Let the butter melt, stirring occasionally. It will immediately foam up and start making brown butter rapidly. The whole process only takes three to four minutes. Run the wooden cooking spoon through the foam often to see when the color of the butter has deepened into a rich brown hue.
Stir the basil into the brown butter sauce.
Now, stir the sliced almonds, paprika, lemon zest, and lime zest into the mixture.
Place the seared grouper fillets into the skillet, and spoon the sauce over the fillets.
Cook for an additional 90 seconds to 2 minutes, or until the fish is cooked through and a digital thermometer reading in the thickest part of each fillet reads at least 145 degrees F.
Remove from heat, and serve immediately.
For best results, leave the stick of butter in the fridge until ready to use. The brown butter sauce absorbs quickly into the fish. So, serve immediately if you want a saucier consistency. This recipe was originally published on April 19, 2017 and updated and republished on April 9, 2022.