Preheat oven to 350 degrees. Remove center of a 12-inch tube pan and cover pan with a double layer of heavy-duty foil. Use a skewer or paring knife to poke 12 small holes in the foil, 2 1/2 inches apart. Gently place a cone in each hole, pushing it down until only about 1 inch of cone is showing.
Make cupcakes: Sift together flour, baking powder, and salt. With an electric mixer on medium-high speed, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating until each is incorporated, scraping down sides of bowl as needed. Beat in vanilla. Add flour mixture in three batches, alternating with two additions of milk, and beating until combined after each. Fill each cone with 2 to 3 tablespoons batter. Bake, rotating pan halfway through, until a cake tester inserted in centers comes out clean, 18 to 20 minutes. Transfer pan to a wire rack to cool completely.
Decorate cupcakes: Tint some of the buttercream pink with gel-paste food color, if desired. Use an ice cream scoop to place buttercream (untinted or pink) on top of cupcake, then top with sprinkles. For "soft-serve" cones, use a pastry bag fitted with only a coupler (or a large plain tip) to pipe buttercream in a swirl over cone, then top with multicolored sprinkles; or, for "sundae" cones, drizzle melted chocolate over buttercream, then sprinkle with peanuts and top with a cherry. For soft-serve "twist" cones, fill a pastry bag fitted with an open-star tip (Ateco No. 828) with untinted and chocolate buttercreams, placing them side by side in bag; pipe two-tone swirls. Serve immediately.