01 - Preheat oven to 350°F. Line a 12-cup muffin pan with cupcake liners.
02 - Whisk together flour, baking powder, and salt in a medium bowl until well combined.
03 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2-3 minutes.
04 - Add eggs one at a time, beating thoroughly after each addition. Mix in vanilla extract.
05 - Gradually add flour mixture to butter mixture, alternating with milk. Begin and end with flour mixture. Mix until just combined.
06 - Divide batter evenly among the 12 muffin cups, filling each about two-thirds full.
07 - Bake for 16-18 minutes, or until a toothpick inserted in the center comes out clean.
08 - Let cupcakes cool in pan for 5 minutes, then transfer to wire rack to cool completely before frosting.
09 - Beat butter until creamy. Gradually add powdered sugar and beat until smooth and creamy.
10 - Mix in watermelon juice, vanilla extract, and food coloring. Beat until light and fluffy.
11 - Reserve a small portion of frosting and tint with green food coloring for the watermelon rind effect.
12 - Frost cooled cupcakes with pink watermelon frosting. Pipe a green ring around edges to mimic rind if desired. Sprinkle mini chocolate chips on top to resemble watermelon seeds.