Add the shrimp and blackened seasoning to a large bowl.
Toss the shrimp to coat it evenly. Set aside.
Preheat a cast iron skillet for 2-3 minutes. That will allow it to get to medium heat.
Add butter and allow it to coat the bottom of the pan. You know your pan is hot when the butter sizzles.
Add the shrimp to the skillet and cook for 1-2 minutes per side. I used jumbo shrimp so they took 2 minutes per side. However, if you are using smaller shrimp then they will cook faster.
Notes
Start with raw, uncooked shrimp. Check the label. The only ingredient should be “shrimp.” Added solutions can affect flavor and how the shrimp sears.
Adjust for store-bought seasoning: I use my blackened seasoning recipe, but packaged blends often contain more salt. Follow the label directions for how much to use per pound.
Turn on the exhaust fan: Blackened spices get smoky in a hot skillet. A little ventilation keeps things comfortable.
Don’t move the shrimp too soon: Once they hit the pan, let them cook undisturbed so the crust forms properly. I like to set a quick timer so I’m not tempted to flip early.
Finish with something bright or creamy: A squeeze of lime adds freshness, or drizzle with a creamy sauce like my bang bang sauce for contrast.