In a food processor combine the 2 Tbsp of Granulated Sugar with the 2 tsp of dried Lavender buds. Pulse until a fine powder is formed. Set aside.
Place softened butter, salt, and vanilla in bowl of stand mixer.
With whisk attachment, beat the butter until light and fluffy.
Add 1 Tbsp of blueberry juice and the lavender sugar mixture.
Add Powdered Sugar a half cup at a time while whipping at medium speed.
Continue to add powdered sugar.
Pour small amounts of berry juice mixing slowly to create the desired shade of purple.
Buttercream should be thick yet easy to spread. If its to thin add more powdered sugar. Too thick, add more berry juice!