Preheat oven to 350 degrees. In a bowl, beat the eggs with the sugar until forming a fluffy and clear mixture. Add milk, oil, and vanilla extract. Continue beating. In another bowl, mix the flour with the baking powder. Add the flour mixed with the baking powder gradually to the egg mixture and stir gently. Divide the dough into two and add chocolate powder to one half. Grease, with oil, and flour in a round pan. Pour the vanilla half of the dough into the center of the pan.

Over it, pour the chocolate half of the dough. Repeat the process, alternating, until you run out of dough.
Bake for 40 minutes or until you pierce the center with a toothpick and it comes out clean. ready to Serve.