Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.

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

In a large bowl, cream the butter and sugar until light and fluffy.

Add eggs one at a time, beating well after each addition. Stir in vanilla extract.

Alternately add the flour mixture and milk to the butter mixture, beginning and ending with flour mixture. Mix until just combined.

Divide the batter into two equal parts. In one part, mix the cocoa powder and boiling water until smooth.

To create the zebra pattern, spoon 2 tablespoons of vanilla batter into the center of the pan, then spoon 2 tablespoons of chocolate batter directly on top. Continue alternating batters in the center until all batter is used.

Bake for 40-45 minutes or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes, then turn out onto a wire rack to cool completely.

Slice and enjoy your beautifully patterned zebra cake!