Preheat your oven at 170 degree celsius. Grease a 8 inch round cake tin with little butter or line the base with parchment paper.
To prepare the eggless sponge cake, first mix together flour, baking soda, powder together in a mixing bowl. Set aside.
In another mixing bowl cream butter using a hand mixer or stand mixer at medium speed still creamy in texture. Gradually add the condensed milk and whisk well using the hand mixer for 1 minute.
Now add sugar and vanilla essence, one last time whisk with the hand mixer for 1 - 2 minutes at medium speed.
Add ⅓ of the flour mixture in the liquid ingredients along with ½ cup of milk. Cut and fold to form a lump-free batter. Add remaining flour and milk. Once again, cut and fold the batter till smooth, evenly combined, and no streaks of flour remain.
Pour the batter in the greased tin. Bake for 35 - 40 minutes in the middle rack of the oven. After 30 minutes cover the tin with an aluminum foil if the top of the cake is browning too fast. At this stage, insert a toothpick and check the cake for doneness as well.
Once baked, remove the cake from the oven, let it sit in the tin for the next 10 - 15 minutes. After cooling down a bit invert the sponge cake onto a wire rack and let it cool down completely at room temperature.
You can serve eggless sponge cake at room temperature or slightly chilled.