Season salmon all over with salt and pepper.
Very lightly spray a large skillet with cooking spray.
Before you turn on the heat, place the salmon fillets in the skillet, skin side down.
Turn heat to medium-high and let the fish cook, pressing into the pan every once in a while, until the skin is super crispy, about 8 minutes.
Turn off the heat, flip the salmon and let it sit in the hot pan for another 2 minutes.
Add lemon juice around the fillets while the salmon cooks for one more minute
Remove the salmon and set aside for serving.
While the pan is off the heat but still hot, add the butter to the pan and swirl to combine into a sauce