Leave butter on the counter to soften until easily maluble. Add softened butter, garlic, cilantro, and lime zest to a small bowl. Mix until combined. Serve soft for easy scooping or store in the fridge for later.
Combine all blackening season ingredients in a small bowl or container and mix to incorporate. This recipe makes 6 tablespoons so you will have plenty extra.
Generously season each salmon filet with blackening seasoning until fully coated on all sides. Squeeze fresh lime juice over each side of each filet and rub it into the salmon. Note: premade blackening seasoning tends to be salty. If you’re salt-sensitive, I’d recommend using a thin dusting.
Heat 1 tablespoon of oil in a cast iron skillet on medium-high heat. Once the pan starts to smoke, sear the salmon, undisturbed, for 3-4 minutes. Flip and sear for 3-4 more minutes. For medium doneness (slightly pink silky center), the salmon should be done. For more well-done salmon that is flakey throughout, sear for 4-5 minutes per side.
Plate and top each salmon filet with a spoonful of cilantro lime butter and serve with a lime wedge and additional chopped cilantro.