Set the oven to 350°F (175°C) and grease both of the 8-inch round pans.
Beat the sugar and butter until they become light and fluffy. Add the eggs and mix them in one at a time. Lastly, add the vanilla.
Combine flour, baking powder, and salt. Then, add the dry mixture and milk alternately.
Split the batter between each of the pans. Bake for 25-30 minutes. Once finished baking, let the pans cool completely.
Stack the layers and fill with a thin layer of white buttercream frosting. Place in the fridge for 20 minutes.
Make a shallow incision around the center of the cake to create the fault line.
Using a piping bag, add colored buttercream into the slot. Apply a thin, white crumb coat over the entire cake so that only a thin slit of color shows.
Refrigerate again so the buttercream stays in place until served.