Red Hot Velvet Cake with Cinnamon Buttercream from Baked

YIELDS
One 8-inch cake
INGREDIENTS
Red Hot Velvet Cake Layers:
1/4 cup dark unsweetened cocoa powder
2 tablespoons red gel food coloring (see note below)
1/4 cup boiling water
6 tablespoons unsalted butter, softened, cut into small pieces
2 tablespoons vegetable shortening, at room temperature
1 2/3 cups sugar
3 large eggs
1 cup buttermilk
1 teaspoon pure vanilla extract
2 1/2 cups cake flour
1 teaspoon fine salt
1 tablespoon cider vinegar
1 teaspoon baking soda
Cinnamon Frosting:
1 1/2 cups sugar
1/4 cup all-purpose flour
1 1/2 cups milk
1/4 cup heavy cream
1 1/2 cups (3 sticks) unsalted butter, soft but cool, cut into small pieces
1 teaspoon pure vanilla extract
2 teaspoons cinnamon
Decoration:
Red Hots (cinnamon imperials) candies

PREPARATION
Red Hot Velvet Cake Layers:
1. Preheat the oven to 325 degrees F. Butter three 8-inch round cake pans, line the bottoms with parchment paper, and butter the parchment. Dust with flour, and knock out the excess flour.
2. In a medium bowl, whisk together the cocoa powder, food coloring, and boiling water. Set aside to cool. In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and shortening until smooth. Scrape down the bowl and add the sugar. Beat until the mixture is light and fluffy, about 5 minutes. Add the eggs, one at a time, beating well after each addition.
3. Stir the buttermilk and vanilla into the cooled cocoa mixture. Sift the flour and salt together into another medium bowl. With the mixer on low, add the flour mixture, alternating with the cocoa mixture, to the egg mixture in three separate additions, beginning and ending with the flour mixture. Beat until incorporated. In a small bowl, combine the vinegar and baking soda and stir until the baking soda dissolves; the mixture will fizz. Add to the batter and stir until just combined.
4. Divide the batter among the prepared pans and smooth the tops. Bake until a toothpick inserted in the center of each cake comes out clean, about 30 minutes, rotating the pans halfway through the baking time. Transfer the cakes to a wire rack and let cool for 20 minutes. Invert the cakes onto the rack, remove the pans, and let cool completely. Remove the parchment.

Cinnamon Frosting:
1. In a medium heavy-bottomed saucepan, whisk the sugar and flour together. Add the milk and cream and cook over medium heat, whisking occasionally, until the mixture comes to a boil and has thickened, about 20 minutes.
2. Transfer the mixture to the bowl of an electric mixer fitted with the paddle attachment. Beat on high speed until cool. Reduce the speed to low and add the butter; beat until thoroughly incorporated. Increase the speed to medium-high and beat until the frosting is light and fluffy. Add the vanilla and cinnamon and continue mixing until combined. If the frosting is too soft, transfer the bowl to the refrigerator to chill slightly, then beat again until it is the proper consistency. If the frosting is too firm, place the bowl over a pot of simmering water and beat with a wooden spoon until it is the proper consistency.

Assemble the cake: Place one cooled cake layer on a serving platter. Trim the top to create a flat surface and evenly spread about 1 1/4 cups of the frosting on top. Top with the next layer, trim and frost the top, then add the third layer. Put the cake in the refrigerator for 15 minutes to firm up the frosting. Frost the sides and top with the remaining frosting. Garnish the cake with the Red Hots and refrigerate again for 15 minutes.