Beat the butter in a large bowl or the bowl of a stand mixer until smooth and creamy.
Add the lemon juice, lemon zest, extract, and salt. Beat to combine.
With the mixer on low, start adding the powdered sugar, 1/2 cup at a time, until all of the sugar has been incorporated. Start mixing on medium. Beat the buttercream until it is light and creamy, 5-10 minutes.
Notes
*The lemon extract adds an addition punch of lemon flavor, but if you don’t have any or don’t want to add it, you can leave it out.You can add a few drops of yellow food coloring to help color the buttercream, but it's not necessary.Nutrition information provided as an estimate only. Various brands and products can change the counts. Any nutritional information should be used as a general guide.