Once baked, remove the cake from the oven and allow it to cool in the pan for 10 minutes. Then, carefully invert the cake onto a wire rack to cool completely before slicing and serving.
In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside this dry mixture for later use.
Start by preheating your oven to 350°F (175°C). Grease and flour a 10-inch Bundt pan to ensure easy removal of the cake.
Beat in the eggs, one at a time, followed by the vanilla extract, until well combined.
In a large mixing bowl, cream together the softened unsalted butter and granulated sugar until light and fluffy.
Transfer half of the vanilla batter to another bowl. Mix the chocolate batter into one half of the vanilla batter until evenly combined, creating the chocolate swirls.
Gradually add the dry ingredients to the wet ingredients in the large mixing bowl, alternating with the milk. Mix until the batter is smooth and well combined.
Place the Bundt pan in the preheated oven and bake for 45-55 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Spoon alternating dollops of the vanilla and chocolate batters into the prepared Bundt pan, creating a marbled effect