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 2-3 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 the flour mixture to the butter mixture in three parts, alternating with the grape juice mixture, beginning and ending with flour. Mix until just combined.
07 - If desired, add a drop or two 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 16-18 minutes, or until a toothpick inserted in the center comes out clean. Let cool in the pan for 5 minutes, then transfer to a 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 a 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.