Simple chocolate zebra tea cake

All the ingredients should better be at room temperature.

1. Lightly whisk the eggs with sugar and vanilla (or vanilla paste).
2. Melt the butter, and cool it to room temperature.
3. Add the sour cream, melted butter and baking soda to the egg mixture. Stir thoroughly.
4. Divide the mass in two parts.
5. Add the flour #1 to one part of the mass, and mix until smooth.
6. Add the flour #2 and cocoa to the second part of the mass, and mix until smooth.
7. Preheat the oven to 356F (180C).
8. Grease a cake mold with butter (oil).
9. Lay out alternately chocolate and light dough. In two or three layers. Maybe in a checkerboard pattern.
10. At the end, draw a zigzag line along the dough with a knife or wooden stick.
11. Sprinkle the cake dough with granola if desired.
12. Bake the tea cake for about 50 minutes. Check for readiness with a wooden skewer.