Preheat oven 350F (175C). line 9-inch round pan with parchment paper and grease bottom and sides. Set aside.
In a bowl, mix flour, salt and baking powder.
In a separate bowl cream butter and sugar. Add eggs, one at the time, beating until combined after each addition. Add vanilla extract and stir until combined.
Alternate adding flour mixture and buttermilk, beginning by adding 1/2 of the flour mixture, then 1/2 of the buttermilk. Then repeat this process. Beat until fully incorporating after each addition.
Divide the butter into two parts. To one part sift cocoa powder and mix until combined.
Drop one large spoonful of vanilla batter in center of the pan, then top with a spoonful of the chocolate batter. Repeat this process until you run out of the batter. At the end give the pan a little shake.
Bake the cake for 45-50 minutes, until a toothpick inserted into the center comes out clean.
Allow to cool for 10 minutes in the pan, release from the pan and allow to cool completely or serve warm.
WHY BUTTERMILK?The use of buttermilk in cakes and cupcakes helps the cake to get a moist and airy texture, in most of my recipes I use buttermilk and indeed you can feel the difference.WHAT CAN WE USE INSTEAD OF BUTTERMILK?If you cannot find buttermilk in your country, you can make a home buttermilk: stir 1¾ cups (420ml) of whole milk with 1¾ tablespoons of vinegar or lemon juice, let stand for 10 minutes before use. If you still prefer not to use buttermilk you can use whole milk instead.HOW TO STORE THE CAKE?The cake can be stored covered, in the fridge, up to 5 days.MORE CAKE RECIPES: