Preheat the oven to 350°F. Grease the bottom of a 10-inch round pan with oil.
Stir the flour, salt and baking powder in a bowl.
In a large mixing bowl, mix the eggs and sugar until smooth and light colored, about two minutes on high speed of a hand mixer. Add the oil and milk, and mix for another minute.
Add the flour mixture and mix just until blended. The batter will be of pouring consistency but not thin. Stir in the vanilla.
Pour half of the batter into another bowl. Add the cocoa powder to one portion and mix until blended.
Assemble the cake: Take two 1/4 measuring cups. Pour a cupful of the white cake batter onto the center of the pan. Then, pour a cupful of the chocolate batter directly on top at the center of the cupful of white cake batter. Repeat until all the cake batter has been poured into the pan.
Bake the cake until a knife inserted at the center comes out clean. Approximately 50 minutes.
Notes
Recipe adapted from Home Cooking Rocks
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.