Allow the butter to come to room temperature before starting.
Beat the butter until creamy, then add in the parsley, red pepper flakes, black pepper, minced garlic, lemon juice and zest.
Mix until well combined.
Scrape down the sides of the bowl and turn the mixture out onto a piece of parchment paper.
Using the back of a spatula, spread out the mixture into a log shape.
Roll the parchment paper up and twist the ends.
Refrigerate for at least 4 hours to allow the flavors to come together.