In a bowl of a mixer beat butter until whipped and smooth.
Add in the powdered sugar and begin mixing on low until it combines, then turn up to medium-high and add the milk, vinegar, vanilla, lemon juice, and salt.
Continue whipping until smooth.
Spread over your favorite desserts.
Multiply to make more frosting; the small batch will spread over an 8" cake. If you want to fill a 2-layer cake, be sure to double or triple the recipe. If you want to pile the frosting high and fill a layer cake, you can use 4x's the recipe for plenty of frosting.
