Mild, firm-fleshed grouper is a great choice for blackening in this simple but flavorful blackened grouper sandwich. Adorned with just a slice of juicy tomato and a good smear of Cajun remoulade on a crisp, buttered bun, this sandwich is casual summer lunch at its finest.
Make the whole thing in only 30 minutes! Or, the seasoning blend and sandwich sauce can be made far in advance (or even store-bought), making for a super-quick and nearly effortless final assembly.
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In my house, we are the blackened fish fan club. We have made blackened salmon probably almost every week since I published the recipe three years ago. My daughter, who just turned 2 this month, will devour a piece and requests it by name. I keep a big jar of homemade blackened seasoning in the pantry at all times — and even with an 8-oz. jar, we go through it pretty darn quickly.
And with this blackened grouper sandwich recipe under my belt now, we may go through it twice as fast! I think it may be my new favorite!
Many recipes on my site are inspired by dishes I’ve had at restaurants around Charleston, and this is no exception. I used to loooove eating the blackened grouper sandwich at Oyster House restaurant downtown, with their crispy Brussels sprouts or perfectly sautéed garlic spinach while sitting on their glorious covered patio.
But alas, the blackened grouper sandwich on their menu has been replaced with a fried snapper one and I’ve been missing it ever since. I had the hardest time finding grouper in the grocery store so I could make my own, so when I finally did I was ecstatic to make this recipe! And honestly, it’s just as good as I remembered.
About this recipe
Grouper is a flaky, mild white fish that doesn’t taste “fishy” at all. It’s firm and has a slightly sweet flavor. It’s the perfect canvas for some flavorful blackened seasoning (as spicy as you like it), charring from the grill, and Cajun remoulade sauce. A juicy slice of tomato and a buttery toasted bun is all you need to complete this delicious sandwich.
What does blackened mean?
Blackening is a cooking technique associated with Cajun cuisine, in which the food (often fish) is coated in melted butter followed by a blend of herbs and spices. Blackened seasoning typically includes salt, pepper, garlic, onion, thyme, oregano, and chili powder. It’s usually cooked in a hot cast iron skillet. The “blackened” color (and name) comes from the toasted spices and milk solids in the butter, not from being burnt.
I recommend making homemade blackened seasoning and Cajun remoulade for this sandwich (ingredients and directions are included in the recipe card) but you may use store-bought in a pinch.
How to Make Blackened Grouper
Dredge the grouper in melted butter followed by your blackened seasoning blend. Pat it down lightly to adhere. Place it on parchment paper to keep the butter and spices from sticking to the cutting board or plate instead of the fish.
Cook 4-5 minutes per side on either a grill (recommended) or a cast iron skillet, until fish reaches 135 degrees Fahrenheit. After removing the grouper will continue to cook while resting to a final temperature of 140 to 145 degrees. I recommend a Thermapen instant read thermometer – it’s super accurate and quick!
Tips for Cooking Blackened Fish Indoors
I recommend grilling your blackened grouper if you have a grill. Why? Well, in my experience, cooking blackened fish on the stovetop tends to result in a very smoky kitchen and has set off my fire alarm on numerous occasions. Sufficient ventilation is key, and unfortunately my recirculating vent hood just doesn’t cut it.
That said, here are some tips for making blackened grouper in your kitchen. I absolve myself of any responsibility for your smoky kitchen and blaring fire alarms if you do this.
Use a cast iron skillet. Cast iron is traditional for making blackened fish. A nice, heavy-bottomed skillet holds heat well (even after adding your cold protein) and gives you that nice sear.
Cook over medium, not high. While it is traditional to blacken fish over high heat, this will almost certainly set off your smoke detector unless you have very powerful ventilation. Butter has a low smoke point, and spices can smoke easily too, so you do the math. I’d rather trade high heat for medium than trade butter for oil when it comes to blackening my fish!
Turn on your vent fan. Yeah, I know, it’s annoying and loud. You know what else is annoying and loud? The smoke detector yelling at you to evacuate your house. Ask me how I know.
Open the windows. Do this before you need to.
Here are some more tips from Cooks Illustrated for blackening proteins without setting off the smoke alarm.
Tips for Grilling Blackened Grouper
Preheat the grill to medium high, then turn down to medium. This gives the grill grates the high heat needed for a perfect sear, but won’t burn your fish before it’s cooked through.
Use a grill mat or tin foil. These nonstick grill mats are my all time favorite grilling accessory. They keep delicate items like fish from sticking to the grill and falling apart, and they’re great for grilling smaller items like cut veggies and shrimp too. They’re reusable for quite a while, and not so expensive you feel like you can’t replace them once a year. Grill mats allow the grill lines to come through onto your fish, which you lose when you use tin foil.
Step by Step Instructions for Blackened Grouper Sandwiches
Mix the blackened seasoning. We’re going to make enough here to use on the fish as well as in the Cajun remoulade.
Make the Cajun remoulade. Apart from chopping some capers, this just involves mixing ingredients in a bowl or measuring cup. This can chill in the fridge so the flavors can meld while you’re cooking the fish.
Cook the grouper. See tips above for grilling (recommended) vs. indoor cooking. For the best of both worlds, you can cook your grouper in a cast iron skillet on an outdoor burner.
Toast the buns. Brush the cut sides of the buns with melted butter and toast for 3-4 minutes on the grill or in the skillet until toasty and browned. You can do this while your grouper is cooking.
Assemble the sandwich. Spread a spoonful of remoulade on each side of the bun. Add grouper and a tomato slice to each sandwich and finish with the top bun.
Additional/alternative toppings: While I like my sandwich with just remoulade and tomato, you can also add a crisp lettuce leaf or step it up with some homemade refrigerator dill pickle slices! You can also swap the Cajun remoulade for easy garlic aioli for a punchy garlic twist.
Expert Tips & Tricks
- You can make the blackened seasoning and the Cajun remoulade sauce up to several days in advance. That way you can just throw the fish and buns on the grill and call it a day!
- When choosing your grouper fillets, look for ones about the same size and shape as your sandwich rolls. They will shrink a little when they cook but not much. Thicker fillets may require cooking an extra minute or two per side.
- Grill the grouper outdoors to avoid a smoky kitchen. If cooking indoors, use your vent fan on high and cook over medium heat. While high heat is more traditional, it’s also more likely to set off your smoke detectors.
- Variations: You may use Garlic Aioli instead of Cajun remoulade if you’d like less of a kick.
What goes well with a blackened grouper sandwich?
I love pairing this with something green! Some ideas are:
- Sautéed spinach and mushrooms
- Parmesan roasted Brussels sprouts
- Classic Southern fried okra with cornmeal, or
- Collard greens
You can’t go wrong with a side of Charleston Red Rice either.
Blackened Grouper Sandwiches with Cajun Remoulade
For the Sandwich
- 4 4-6 oz. grouper fillets
- 8 tablespoons salted butter melted
- 6 tablespoons homemade blackened seasoning or use recipe below
- 4 sandwich buns
- 1/2 cup Cajun Remoulade or use recipe below
- 1 tomato large
For the Cajun Remoulade
Homemade Blackened Seasoning
- 2 tablespoons paprika or smoked paprika
- 1 tablespoon chili powder
- 1 tablespoon kosher salt
- 1 tablespoon garlic powder
- 1 tablespoon dried oregano
- 1 tablespoon dried thyme
- 1 1/2 teaspoons onion powder
- 1 1/2 teaspoons black pepper
- 3/4 to 1 1/2 teaspoons cayenne pepper to taste
- If making your own seasoning blend (recommended), mix together all spices for homemade blackened seasoning in a small bowl. (Can be done days or even weeks in advance)
- If making your own remoulade (recommended), mix together all ingredients for Cajun remoulade in a medium bowl. Set aside in the refrigerator. (Can be done up to a week or two in advance)
- Brush each half of the sandwich buns with 1 tablespoon melted butter. Set aside.
- Dredge the grouper fillets on both sides in the remaining butter, followed by the blackened seasoning.
To grill (recommended)
- Preheat gas grill over medium high heat for 10 minutes. Then turn down to medium. Lay down a grill mat or tin foil on top of grill grates and grill grouper 4-5 minutes per side or until internal temperature reaches 135 degrees Fahrenheit. Thicker fillets may require an extra minute or two on each side. Fish will continue to cook while resting to a final temperature of 140 to 145 degrees.
- Meanwhile, place buns buttered-side down on grill rack, if you have one. Let them toast for 4-5 minutes or until you have nice toasty grill lines. If cooking directly on grill grates, you will need to turn the heat down underneath the buns and cook for less time.
To cook indoors
- Turn off your fire alarm if possible. Turn your vent hood on high and open any nearby windows. Preheat a cast iron skillet to medium (not high) and cook grouper for 4-5 minutes per side or until internal temperature reaches 135 degrees Fahrenheit. Thicker fillets may require an extra minute or two on each side. Set aside. Fish will continue to cook while resting to a final temperature of 140 to 145 degrees.
- Toast buttered sides of buns in skillet for about 4 minutes or until toasty brown.