Marble Cake: A Swirl of Flavors in Every Bite

Preheat your oven to 350°F (175°C). Grease and flour a 9×9-inch square baking pan or an 8-inch round cake pan. Alternatively, you can line the bottom with parchment paper for easy removal.
Mix dry ingredients:

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
Cream the butter and sugar:

In a large mixing bowl, beat the softened butter and sugar together using an electric mixer or stand mixer on medium speed until light and fluffy, about 3-4 minutes.
Add the eggs and vanilla:

Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract.
Combine the wet and dry ingredients:

Gradually add the dry ingredients to the butter mixture, alternating with the milk. Start and end with the dry ingredients. Mix just until combined.
Prepare the chocolate batter:

In a separate bowl, combine the cocoa powder and hot water to make a smooth chocolate paste. Add this paste to half of the batter and stir to combine. If you’re using chocolate chips, fold them into the chocolate batter.
Create the marble effect:

Drop alternating spoonfuls of the vanilla and chocolate batters into the prepared pan. Using a butter knife or a skewer, gently swirl the two batters together to create a marbled effect. Be careful not to over-mix; a few swirls are all you need for a beautiful marble pattern.
Bake the cake:

Place the pan in the preheated oven and bake for 30-35 minutes, or until a toothpick inserted into the center of the cake comes out clean. If the cake is browning too quickly, cover it loosely with aluminum foil.
Cool and serve:

Let the cake cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely. Once cooled, slice and serve.
Serving and Storage Tips: