Let the butter soften until it is mashable with a spoon.
Combine sugar and butter together using a hand or electric whisk/beater. Whisk well until light and fluffy.
Add the eggs one at a time, beating well after each addition.
Sift together the maida, salt and baking soda, ensuring no lumps.
Gradually add this to the egg mixture, alternating with milk. Stop whisking and fold this mixture gently with a spatula until all the batter is fully incorporated and smooth. Do not over beat.
Add vanilla essence and blend well.
Take a cake tin and grease it with some butter or oil. Sprinkle some maida on a greased baking tin.
Pour the prepared mixture into the tin and place it in the prepared pressure cooker over the pot holder/ring.
Cover the cooker with the lid (without the gasket and weight).
Bake on low flame for 50-60 minutes.
To test, put in a knife, it should come out clean, showing that it is fully baked.
Take it out and let it cool completely.
Once cooled, invert the cake on a wire rack and let it cool fully before slicing it.