Instructions

• Preheat the oven to 180°C / 350°F. Grease two 8-inch (20 cm) round cake pans and line the bottoms with parchment paper (optional) for easier removal. Set pans aside.
• In a large mixing bowl, whisk together 3 cups all-purpose flour, 2 cups sugar, 1 teaspoon salt, and 2 teaspoons baking soda until evenly combined.
• Add the wet ingredients to the dry mixture: 2 teaspoons white vinegar, 1/2 cup + 2 tablespoons oil, 2 teaspoons vanilla extract, and 2 cups water. Mix on low-to-medium speed (or stir) until the batter is smooth and uniform, scraping the bowl sides as needed.
• Divide the batter evenly between two medium bowls. Stir 1/4 teaspoon yellow food coloring into one bowl and 1/4 teaspoon red food coloring into the other bowl until the color is even.
• Pour the yellow batter into one prepared pan and the red batter into the other prepared pan, smoothing the tops with a spatula.
• Bake both pans in the preheated oven for 25–27 minutes, or until a toothpick or skewer inserted into the center comes out clean or with a few moist crumbs.
• Remove the pans from the oven and let the cakes cool in the pans for about 10 minutes. Run a knife around the pan edges, then invert the cakes onto wire racks and remove the parchment. Let the cakes cool completely before slicing.
• Once completely cool, use a long serrated knife or a cake leveler to slice each cake horizontally into two even layers, yielding four cake layers total (two red layers and two yellow layers). Place the layers on separate plates or racks, keeping them in order.
• To make the frosting, place 6 cups powdered sugar and 2 cups softened butter in the bowl of a stand mixer or a large mixing bowl. Beat on low speed until the sugar is incorporated, then increase speed to medium and beat until the mixture is smooth and creamy.
• Add 2 teaspoons vanilla extract, then add the 1/4 cup heavy whipping cream gradually while mixing until the frosting is combined and reaches a spreadable consistency. Stop and scrape the bowl as needed.
• Divide the frosting into two bowls. In one bowl stir in 1/2 teaspoon red food coloring until evenly tinted; leave the other bowl plain (uncolored).
• Assemble the cake on a flat serving plate or cake board: place one red layer down as the base, spread an even layer of plain frosting over it, then place a yellow layer on top. Repeat with the next plain-frosting layer and the next red layer, ending with the final cake layer on top.
• Use the red-tinted frosting to cover the top and exterior sides of the stacked cake, smoothing with an offset spatula or knife. If you prefer, reserve a thin crumb coat of red frosting, chill 10–15 minutes, then finish with a final coat.
• Let the assembled cake sit for several minutes (or chill 15–30 minutes for cleaner slices) to set the frosting, then slice and serve.