Preheat the oven at 170 C / 340 F
Grease and line with parchment paper 3 x 6-inch round or 2 x 8-inch round baking pans
Prepare wet ingredients - Add the hot water to the cocoa powder and let cool slightly. Then add the oil, eggs, sour cream, and vanilla - use a whisk to ensure there are no lumps
Prepare dry ingredients - In another bowl combine the flour, baking powder, and sugar.
Combine wet to dry ingredients - pour the cocoa mixture into the flour mixture.
Use a whisk to ensure everything is well combined.
Pour batter into the prepared baking pans
Bake in the preheated oven for 30 to 40 minutes or until a skewer inserted in the center comes out clean.
When done - cool in the pan for 10 minutes.
Remove from the pan and cool completely on the wire rack.