The Best Blackened Grouper (Cast-Iron Skillet)

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In this recipe for Blackened Grouper, the blackening seasoning infuses the fish with a subtle spicy flavor that hits all of the right notes. Then, a quick sear in a cast-iron skillet seals in the grouper’s briny sweetness for a truly delicious main dish.

Blackened grouper on a white plate with grits.

A quick seafood recipe that takes less than 20-minutes to prepare, my incredible Blackened Grouper recipe is simple enough for a weeknight dinner and fancy enough for company.

Blackening is a cooking method used for fish and other meats where it is coated in butter and a blend of spices and herbs; then it is pan-seared in a screaming hot cast-iron skillet. The high heat chars the butter and spice mix and creates a brownish-black crispy and tasty crust. Blackening first became popular in New Orleans by Chef Paul Prudhomme.

There are many different recipes for blackened fish seasoning, and while there are many similarities, what sets this recipe apart is a touch of brown sugar, which serves to balance out the spicier spices. Grouper has a delicate flavor, and too much heat will hide its natural sweetness.

I always blacken my fish in a cast-iron skillet, but you can also cook it on the grill or in the oven.

Here’s what you will need:

A cutting board with herbs, spices and fish fillets.

Grouper fillets: the star of this show. You need four skinless grouper fillets, four to six ounces each, that are one-half of an inch thick.
Spices: you will need paprika, cayenne pepper, black pepper, ground cumin, garlic powder, onion powder, and kosher salt for the blackened fish seasoning.
Herbs: dried oregano and dried thyme are key ingredients in the blackened seasoning.
Brown sugar: my secret ingredient in the seasoning. Not only does it add just a touch of sweetness, but it also is what makes the crust crispy.
Butter: I use unsalted butter. The butter coats the fish, which helps the seasoning stay put, and the grouper is also cooked in the butter, which adds richness to the dish.
Lemon: fresh lemon and fish go together, and a small squeeze of this fragrant and flavorful citrus enhances all of the other flavors and brings them all together.

Here’s how to make it:

To make the blackened fish seasoning, combine all ingredients in a small bowl, and mix well. Set aside.
Pat dry the fillets with a paper towel.
Melt two tablespoons of butter and use a pastry brush to coat both sides of the fillets.
Top each fillet with about a tablespoon of the seasoning mix and rub it with your fingers. Turn the fillets over and repeat.
Add three tablespoons of butter to a cast-iron skillet over medium-high heat.
When the butter has melted, and the skillet is hot, add the fish and cook undisturbed for three minutes.
Use a fish spatula to turn the fish over and cook for another three to four minutes or until the fish is done. The fish is done with the flesh turns opaque and flakes easily when pierced with a fork.
Top each fillet with a squeeze of lemon juice and serve immediately.

Blackened grouper fillet with grits and broccoli on a plate.

Frequently asked questions:

What to serve with it?

In my world, you can’t have cooked fish without Cheese Grits. After that, my rules aren’t quite as strict, and there are lots of other options. Coleslaw is always a good choice, as is my Broccoli Slaw with Ramen Noodles, Smoked Baked Beans, or Southern Broccoli Salad. And, just in case you don’t have grits, my Homemade French Fries or Crispy Fried Onion Rings work well too. Oh, and don’t forget my Southern Hush Puppies.

What does grouper taste like?

Grouper has a very mild, sweet, briny flavor and tastes like a day at the beach. You can almost smell the sea air. It also has firm, white flesh and, when cooked, forms large tender flakes. It is most definitely one of the best-tasting fish harvested in the Gulf of Mexico, along with Red Snapper and Mahi-Mahi. Grouper is also very similar in taste to seabass or halibut.

What’s the best fish to blacken?

Besides Grouper, Mahi Mahi is wonderful, and Red Snapper, Halibut, Tilapia, Catfish, or any firm white fish also work well. When buying your fish, plan on four to six ounces of fish per person.

How do you store fresh fish?

Fresh fish is extremely perishable, and it’s best to purchase your fish the day you plan to cook it. However, it also can be stored covered in your refrigerator for up to two days. If you are not planning to cook it within two days, you should freeze it. Freeze fresh fish in an airtight container or plastic freezer bag to prevent freezer burn. You can safely freeze it for up to two months without any loss in quality. To thaw it, place it in the refrigerator the night before you plan to cook it.

Sharon’s tips:

This recipe for blackened grouper will produce a moderate amount of smoke. Before cooking, be sure to turn your kitchen exhaust fan on high or open a window.
The cooking times shown are for fillets that are one-half of an inch thick. If your fillets are thicker or thinner, they will take more or less time to cook.
If you have any leftover blackening seasoning, store it in a small airtight container for future use.
In a pinch, you can substitute purchased blackening seasonings. I have used both Old Bay and Paul Prudhomme blends, but I always add a touch of brown sugar.
This recipe, as written, is a little spicy. If you would like to tone it down a bit, reduce or leave out the cayenne pepper.
You can substitute any firm white fish fillets for the grouper.
Leftover fish can be used to make fish tacos or homemade fish cakes.