01 - Preheat oven to 350°F. Line a 12-cup muffin pan with cupcake liners.
02 - In a medium bowl, whisk together the flour, baking powder, and salt until well combined.
03 - In a large bowl, beat the softened butter and granulated sugar until light and fluffy, approximately 2-3 minutes.
04 - Add eggs one at a time, beating thoroughly after each addition. Mix in the vanilla extract.
05 - Gradually add the flour mixture to the butter mixture, alternating with milk. Begin and end with the flour mixture. Mix until just combined, being careful not to overmix.
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. Cool cupcakes in pan for 5 minutes, then transfer to wire rack to cool completely.
08 - Beat the softened butter until creamy. Gradually add powdered sugar and beat until smooth and well incorporated.
09 - Add watermelon juice, vanilla extract, and food coloring if desired. Beat until light and fluffy.
10 - Divide a small portion of frosting and tint with green food coloring for creating the rind effect around cupcake edges.
11 - Frost cooled cupcakes with watermelon frosting. Garnish with mini chocolate chips to resemble watermelon seeds. Optionally pipe a green ring around edges to mimic the rind.