Beat with wire two eggs together with the sugar to form a homogeneous mixture, add a teaspoon of baking soda and stir the mixture again. Then add the oil and mix well again products to better absorb the oil. Then add the yogurt and mix again. Finally, add the flour and vanilla 3-4 times by gently stirring until a uniform mixture. From this mixture and take 4-5 tbsp cocoa mix them. Take the cake pan and rub with oil (I always paint my form with butter), then sprinkle well as with flour and shake excess. Cover the bottom half of the mixture. On it evenly spread colored cocoa mixture and cover with the other half of the light mixture. Bake in pre-heated oven at 170C degrees until ready. Try that now ready your cake with a wooden skewer. pierce it and then remove it if no kebab dough, then your cake is ready. It is good to sprinkle the finished cake with powdered sugar while still warm. Then sugar sticks best surface. From this mixture can also make and base for homemade cake, to cut in two and garnish with cream as desired. Maybe if you want to spill the mixture into molds for muffins and get small individual cakes.