Blackened Mahi Mahi with Pineapple Salsa

Blackened mahi mahi with pineapple salsa doesn’t need a spice cabinet emptied out to get a proper blackened crust. Mahi mahi seared in Cajun seasoning instead of a homemade 8-spice blackening rub, topped with a 4-ingredient pineapple salsa built on store-bought pre-cut pineapple — one skillet, ready in 20 minutes. Every version of this recipe measures out its own blackening blend from individual spice jars, which is a real technique if blackening is a regular thing in the kitchen and all those spices are already stocked. For a Tuesday dinner, a single jar of Cajun seasoning already sitting in the pantry covers the same ground.

Cajun Seasoning Is Already a Blackening Blend

This is the actual insight behind the whole recipe. Blackening spice and Cajun seasoning share almost the exact same base — paprika, garlic, onion, cayenne, oregano, thyme — because blackening as a technique grew directly out of Cajun and Creole cooking. Reaching for a jar of Cajun seasoning instead of measuring out seven individual spices isn’t a shortcut that changes the flavor, it’s using the actual thing the homemade blend is trying to replicate. If Cajun seasoning is already stocked for other recipes on this site, there’s nothing new to buy here.

Pat the Fish Completely Dry First

This step gets glossed over in a lot of recipes, but it’s the difference between a proper blackened crust and seasoning that just steams off in the pan. Any surface moisture on the fish turns to steam the second it hits a hot skillet, and that steam pushes the seasoning off before it has a chance to char. A few extra seconds with a paper towel before the Cajun seasoning goes on is what actually gets that deep, dark crust.

The Pan Needs to Be Genuinely Hot

Mahi mahi is a firm, meaty fish that can handle real heat without falling apart, which is exactly what blackening requires. Medium-high, with the oil shimmering before the fish goes in, is the target — a pan that’s not hot enough just cooks the fish through without ever developing the dark, almost-charred exterior blackening is named for. Three to four minutes per side is enough; mahi mahi cooks fast, and the visual cue is a fillet that flakes easily with a fork.

Store-Bought Pineapple Skips the Hardest Part of the Salsa

Cutting down a whole pineapple is genuinely one of the more annoying prep tasks in home cooking — trimming the top and bottom, slicing off the spiky skin, cutting around the tough core. Pre-cut pineapple from the produce section skips all of it, and diced small, it behaves exactly the same in the salsa as fresh-cut pineapple would. This is the ingredient that does the most work toward keeping this recipe at 8 total ingredients instead of the double-digit lists most competing versions run.

Let the Salsa Sit While the Fish Cooks

The pineapple, onion, jalapeño, cilantro, and lime juice benefit from a few minutes together before serving — the acid from the lime softens the onion slightly and pulls the flavors together in a way that’s noticeably better than salsa served the second it’s mixed. Making it first and letting it sit while the fish cooks means it’s ready exactly when the fish is, with no extra waiting built into the timeline.

Storage

The salsa can be made up to a day ahead and keeps 2 days refrigerated on its own — it holds up well since there’s no avocado or anything else prone to browning in it. The fish is best eaten the day it’s cooked; like most seafood, it loses its texture and gets a little rubbery reheated. For more ways to use Cajun seasoning already in the pantry, High Protein Pork and Cauliflower Rice Bowls and Blackened Chicken and Quinoa Power Bowls both use the same jar for a completely different protein.