Keep the butter at room temperature for several hours so it softens.
Preheat the oven to 320 °F (160 °C).
Grease one 10-inch round cake pan, and place the baking paper on the bottom.
In a large bowl, combine the flour, powdered sugar, granulated sugar, baking powder, cocoa powder, and salt.
In a separate bowl, whisk together the eggs, buttermilk, red food coloring, vanilla extract, and apple vinegar.
Slowly add the wet ingredients to the dry ingredients, including softened butter, and mix until just combined. This will take about 3 minutes.
Bake the cake for 55 minutes. When it’s done, leave it to cool completely.Â