2 ice cream cone baking racks; ice cream scoop; piping bag with round tip
Preheat the oven to 350 degrees F. Place the ice cream cones in 2 cupcake cone baking racks set over 1 parchment-lined baking sheet.
Place the butter and sugar in the bowl of a stand mixer and beat on medium speed until light and fluffy, about 5 minutes. Add the eggs one at a time, beating after each addition until blended. With the mixer on low speed, gradually add the flour alternating with the milk and mix until incorporated. Beat in the baking powder, salt and vanilla. Fold in 1 cup of the rainbow sprinkles.
Divide the batter evenly among the cones with an ice cream scoop, filling 2/3 to completely full. Bake until a toothpick inserted in the center comes out clean, 35 to 40 minutes. Cool for 30 minutes.
Transfer the buttercream to a piping bag fitted with a round tip or a large ziptop bag with the corner snipped off. Pipe a swirl of the vanilla buttercream on each cooled cupcake cone. Chill the frosted cupcakes in the refrigerator for at least 30 minutes.
Microwave the chocolate chips and coconut oil in a microwavable bowl on high in 30-second intervals, stirring until melted. Allow to cool slightly. Pour 1/2 teaspoon of the mixture in the center of each cupcake, allowing the chocolate to drip down the frosting. Working quickly, top each with a few rainbow sprinkles and a maraschino cherry.