Preheat your oven to 350°F (175°C). Grease your pan and line it with parchment paper if available.

In a bowl, whisk together the flour, baking powder, baking soda, and salt.

In another bowl, beat the butter and sugar until fluffy, about 2 to 3 minutes. Add eggs one at a time, followed by the vanilla extract.

Gradually add the dry ingredients in portions, alternating with the buttermilk until the mixture is smooth and thick.

Split the batter into two bowls. Sift cocoa powder into one and mix. If too thick, add a splash of milk.

For a swirled effect, alternate dollops of the vanilla and chocolate batter in the pan and gently swirl. For a cleaner look, spread evenly.

Bake for 28 to 35 minutes for a 9x13 pan, or 24 to 30 minutes for two 8-inch rounds. A toothpick should come out with a few moist crumbs.

Allow the cake to cool completely before glazing.

For the quick black and white glaze, mix powdered sugar, milk, and vanilla for the vanilla side and cocoa powder for the chocolate side.

Spread the vanilla glaze over half of the cake and the chocolate glaze over the other half.

For a neat look, run a spoon along the center line.