Bring the unsalted butter to room temperature.
Cream the unsalted butter in the stand mixer using the paddle attachment.
In a small dish, combine three tablespoons of warm milk with two teaspoons of beet powder. Stir until the beet powder is dissolved.
Add the beet powder food dye into the butter and mix on medium until well combined. Use a rubber spatula to scrape the sides as needed.
Add in the powdered sugar and vanilla extract. Cover the mixer with a towel and mix on low speed until the powder has started to mix with the burgundy colored butter.
If needed, add up to two more teaspoons of beet powder into the mixing bowl. You do not need to make the paste, as there is now enough liquid in the buttercream to help it dissolve. Continue to mix on low until the powder is dissolved completely. Add more powdered sugar to help bring it together or offset a beet taste, if needed.