Place the red onion, jalapeno, cilantro leaves and lime juice in a bowl. Set aside. Sprinkle the snapper filets with
Set a large skillet over medium heat. Once it’s hot, add the olive oil and the corn kernels. Cook for 5 minutes, or until the corn is just tender. Leave the heat on while you transfer the corn to the bowl with the other salsa ingredients and give everything a big stir.
Return the pan to the heat and melt the butter. Add the snapper filets and half-cover the skillet, allowing some steam to circulate and some to escape. If your skillet doesn’t have a cover, tent it lightly with aluminium foil or use the top from one of your stockpots.
Cook the snapper for 3-4 minutes, then carefully and gently flip the filets and cook for an additional 3-4 minutes or until it’s just cooked through at the thickest part. Remove to a serving plate or plates and top with the corn salsa.