Beat the sugar and yogurt for 5 minutes on high speed. Add baking powder and baking soda, beat in on low, and allow to stand for 3 minutes. You will find that bubbles appear.
Sift cocoa powder & flour together 2-3 times.
Beat in the oil and vanilla extract. Next, slowly add the flour mixture in 4 lots, blending in well after each addition.
Using an ice cream scoop, pour two scoops of vanilla mixture into pan. Now alternate and pour one scoop of chocolate mixture on top of vanilla mixture. Continue to alternate between vanilla and chocolate layers until bundt pan is filled.
Bake at 200 C for 10 minutes, reduce temperature to 170-180 C and bake for 45-50 minutes or till a toothpick inserted into the cake comes out clean.
Cool the cake for 30 minutes and then overturn onto a plate.
Wait for at least 2 hours before slicing it, else it doesn't slice neatly.