Directions

1. Preheat oven to 350 degrees F (175 degrees C). Grease and flour 2 9-inch cake pans. In a bowl, sift cake flour with baking soda.
2. Mash the vegetable shortening with 1 1/2 cup of sugar in a large bowl until thoroughly combined, and stir in the eggs, one at a time. Pour the red food coloring into a small bowl, and fill the empty food coloring container with water; add the water to the food coloring. Stir in cocoa powder to make a paste, and mix the paste into the shortening mixture.
3. Stir the buttermilk, salt, vanilla extract, and apple cider vinegar in a bowl, and mix into the colored shortening mixture, alternating with the flour mixture, until well combined. Scrape the batter into the prepared cake pans.
4. Bake in the preheated oven until a toothpick inserted into the center of a cake comes out clean, 30 to 35 minutes. Allow the cakes to cool completely.
5. To make frosting, whisk together the milk and all-purpose flour in a saucepan until the mixture is free of lumps, and bring to a simmer over medium-low heat. Cook, whisking constantly, until the mixture is thick, about 1 minute. Pour the thickened sauce into a mixing bowl, and chill until completely cooled, at least 30 minutes. When cold, place the butter into the mixture, and beat with an electric mixer to combine; add the vanilla extract and 2 cups of sugar to the bowl, and beat with the mixer set on Medium speed until the frosting is light and fluffy, about 3 minutes.