Preheat your oven to 180 C. Butter and flour a bundt pan.

Mix the tablespoon of vinegar with the cup of milk. Stir and keep it aside.

In a bowl, sift or whisk together the flour, baking soda, baking powder and vanilla. Keep aside.

In a large bowl, beat butter and sugar until light and fluffy. This will take few minutes.

Add the eggs one by one and beat well after each egg. Scrape the bowl as needed.

Add the vanilla and beat well.

Now add the flour mixture and buttermilk alternately. First add ⅓ of the flour mixture, beat until incorporated, then ½ of the butter milk and beat, next ⅓ of the flour mixture, beat, then remaining ½ buttermilk, beat and then the last ⅓ of flour mixture and beat until just incorporated.

Remove half of the batter into another bowl. It doesn't have to be exact.

Whisk in the cocoa powder, vinegar and then the red food colour.

Into your prepared pan, using a icecream scoop or large spoon/ladle, place dollops of vanilla batter leaving gaps in between. In these gaps, now place dollops of red velvet batter.

Over the red velvet batter place dollops of the remaining vanilla batter and over the vanilla batter dollops, place dollops of the remaining red velvet batter.

Now take a knife or a skewer. Gently put in into the batter, almost reaching the bottom of the pan at one corner or point. Now move it gently in a zig zag across the batter until you reach your starting point again. Don't over do this or the marbling won't be clear.

Bake at 180 C or 350 F for 35 to 45 minutes until the cake springs back when pressed.

Cook in pan for 5 minutes and then unmould. Cool completely on a wire rack.