First need to preheat pressure cooker. For that, spread salt at the base of cooker.
Place a plate or some stand at the center of cooker over the salt.
Remove the gasket (rubber ring) & vent weight (whistle) from the lid of cooker.
Close the lid & place cooker on gas stove on low flame for preheating. Cooker needs to be pre-heated for atleast 10 minutes.
By that time, prepare the batter. Take a bowl & add oil, sugar & curd/yogurt in it. Mix it. This is not necessary to dissolve the sugar completely.
Place a sieve over the bowl and add all purpose flour, baking powder, baking soda and salt.
Sieve them into the bowl.
Add lemon juice and lemon zest. What is lemon zest is explained in the notes below.
Mix them by adding milk. But do not overdo.
Take a bowl and grease with oil. We have used regular steel bowl kept in kitchen. You can use steel glasses or katories too.
Pour the batter in the bowl. If using glasses or katories, don't not fill them to the top. Only fill 3/4 of them otherwise while baking, batter when rise, may ooze out.
Open the pressure cooker and place the bowl in the center over the plate or stand. Be careful, this time cooker is extremely hot.
Close the lid of cooker. Closing means proper closing which you close while cooking regular food. Do not just put the lid on cooker with a fear of its getting burst. As gesket (ring) & vent weight (whistle) has been removed so there's nothing to worry. Bake for 35-40 minutes or until done on low flame.
To check whether the cake is ready or not, insert a toothpick or knife in the cake. If the toothpick comes out clean, it means your cake is ready.
Take the cake out of pressure cooker and let it cool completely.
Gently run the knife on all the sides of cake so that it easily comes out.
Take the cake out in a plate and enjoy after cutting into slices.