Preheat the oven to 350° and spray a muffin tin before lining with cupcake liners. Set aside.
In a medium bowl, whisk together the flour, sugar, baking powder, baking soda, lavender buds, and salt.
Add the buttermilk, milk, vanilla, lavender extract, and oil to the dry ingredients and beat with the paddle attachment of a stand mixer or a hand mixer just until fully combined. In a separate bowl whip the egg whites until you get medium-stiff peaks and gently fold into the batter.
Scoop the colored batter into the cupcake liners until they are 2/3 of the way full. Bake for 20-25 minutes until a toothpick comes out clean and the tops of the cupcakes bounce back when lightly pressed.
In the bowl of a mixer add the butter. Use the paddle attachment to beat the butter for 1-2 minutes until it is smooth and creamy.
Add the lemon juice, lemon zest, salt, and powdered sugar and mix on low until most of the sugar has been absorbed by the butter. You may need to scrape down the sides and bottom of the bowl a few times.
Add the milk 1 tablespoon at a time on medium-low. Scrape down the sides of the bowl and then beat on medium-high for 2 minutes, or until the frosting is looking quite white and fluffy. If you would like, tint the frosting light purple in color.
Pipe on top of the cooled cupcakes and top with lemon zest and lavender buds.