01 - Preheat oven to 350°F. Line a 12-cup muffin tin with cupcake liners.
02 - In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
03 - In a large bowl, beat butter and sugar together until light and fluffy, approximately 2 to 3 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in vanilla extract.
05 - In a small bowl, combine sparkling pink grape juice and milk.
06 - Add flour mixture to butter mixture in three parts, alternating with juice mixture—beginning and ending with flour. Mix until just combined.
07 - If desired, add one to two drops of pink food coloring and gently mix for a rosy hue.
08 - Divide batter evenly among cupcake liners, filling each approximately two-thirds full.
09 - Bake for 16 to 18 minutes, or until a toothpick inserted in the center comes out clean. Cool in pan for 5 minutes, then transfer to wire rack to cool completely.
10 - Beat butter until creamy. Gradually add powdered sugar, beating until fluffy. Add sparkling pink grape juice, vanilla, salt, and one drop of pink food coloring if using. Beat until smooth and spreadable.
11 - Pipe or spread buttercream onto cooled cupcakes. Decorate with sprinkles or edible glitter if desired.