Why choose between chocolate and vanilla when you can have both thanks to this easy Marble Cake recipe!
In a measuring cup, whisk the milk and vinegar together, and set aside to curdle. In a large bowl, whisk the flour, baking powder, and salt until well combined.
In a second bowl, use a hand mixer or stand mixer fitted with a paddle attachment to cream the butter and sugar together until smooth.
Add the eggs to the butter mixture, and beat to combine. Beat in the sour cream and vanilla extract, scraping down the sides of the bowl as needed.
With the mixer on low speed, slowly pour the dry ingredients into the bowl of wet ingredients. Mix until just combined.
Transfer 1 cup of the cake batter to a separate, clean bowl. Add the vegetable oil and cocoa powder, stirring just until combined.
Spread a thin layer of the plain vanilla batter in the bottom of a prepared loaf pan. Alternate spoonfuls of the chocolate batter and vanilla batter on top. Repeat until all of the batter has been used. Then, use a knife or wooden skewer to gently swirl the batter around, creating a marbled effect.
Place the cake in a preheated oven, and bake until the batter has risen and a toothpick can be inserted into the center and comes out clean.
Allow the cake to cool in the pan. Then, invert it onto a plate, and add your favorite icing, if desired before serving.