Prepare a 7 inch cake pan and line it with butter/oil and line a butter paper. Preheat the oven for 10 minutes at 150 degree C.
Sieve together dry ingredients, Flour, baking soda, baking powder and coco powder and keep it aside.
Take another bowl add egg and beat. Into it add powdered sugar and beat till creamy and fluffy add in vanilla essence and mix.
Fold in the dry ingredients and milk into the egg sugar mix alternatively in two times.
Add in oil and mix.
Pour the batter in the prepared tin and tap the bake tin to release air bubbles if any, and bake in a preheated oven for 30-40 mins or until a tooth pick inserted comes out clean. Allow it to cool for 5minutes before demoulding it. Cool the cake completely before frosting.
Recipe by Kerala Cooking Recipes at https://www.keralacookingrecipes.com/chocolate-sponge-cake-recipe/