Classic Cake with Fudge Layer

Ingredients:
1.5 cups flour
1 tbs baking powder
3 large eggs
1 cup powdered sugar
1/2 cup milk
1/2 cup oil
1 tsp vanilla extract
3 tbs cocoa powder

Method:
Grease and line a 9" round cake tin.
Sift the flour, baking powder, sugar a couple of times.
Beat the eggs and add the milk, oil and vanilla till well combined.
Gradually beat in the flour on low speed just until combined.
Divide the mixture into two and mix cocoa powder in 1/2 cup.
Preheat the oven to 350F.
Pour the cake mix in the greased pan and add the cocoa on top of it a random order.
Gently swirl it with a knife.
Cook for 45 minutes or toothpick inserted in the center comes out clean.