Sift the flour through a sieve, quench the baking soda with vinegar, and line the baking pan with parchment.
Beat the eggs with sugar with a mixer, melt the butter, add the beaten eggs, mix, add sour cream and mix with the mixer at low speed. Add flour and slaked soda to the egg mixture and stir.
Divide the resulting dough in half and place in two bowls. Add 2 tablespoons of cocoa to one part, 2 tablespoons of flour to the other, you will get two types of dough, dark and light.
Place 2 tablespoons of dark dough in the center of the baking dish, place 2 tablespoons of light dough on top, and place all the dough one by one. It will begin to spread, circles of two colors will form, resembling a zebra. Place the pan in a preheated oven, bake for 45 minutes at 180C. Check readiness with a wooden stick; it should be dry.
Place the finished pie on a wooden surface, cut into portions, serve with chocolate topping and a cup of hot tea.