Preheat the oven to 350 degrees F (175 degrees C). Grease and flour two 9-inch round cake pans; line bottoms with parchment paper. Place a medium bowl in the refrigerator to chill.

Whisk flour, sugar, cocoa, baking powder, baking soda, and salt together in a large bowl. Add eggs, milk, oil, and vanilla; beat until combined. Pour cake batter into the prepared pans.

Bake in the preheated oven until a toothpick inserted in the centers comes out clean, about 35 minutes. Cool layers in pans on wire racks for 10 minutes. Run a paring knife around edges to loosen and invert carefully onto racks to cool completely, 1 to 2 hours.

While cake layers bake, drain cherries for topping, reserving 1/2 cup juice. Combine reserved juice, cherries, sugar, and cornstarch in a 2-quart saucepan. Cook, stirring constantly, over low heat until thickened. Stir in vanilla. Let cool at room temperature for 30 minutes. Transfer to the refrigerator to cool completely before assembling cake.

Combine whipping cream and confectioners' sugar for frosting in the chilled medium bowl. Beat with an electric mixer at high speed until stiff peaks form.

Split each cake layer in half horizontally using a long serrated knife. Tear one layer into crumbs; set aside. Gently brush loose crumbs off top and sides of remaining layers using a pastry brush or your hands. Reserve 1 1/2 cups frosting for piping decorations on cake; set aside.

To assemble, place one cake layer on a cake plate. Spread with 1 cup frosting; top with 3/4 cup cherry topping. Top with second cake layer; repeat layers of frosting and cherry topping. Top with third cake layer and frost sides of cake.

Pat reserved cake crumbs onto sides of cake. Spoon reserved 1 1/2 cups frosting into a pastry bag fitted with a star decorator tip. Pipe around top and bottom edges of cake. Spoon remaining cherry topping on top of cake.

Store covered in the refrigerator until ready to serve.