Beat the egg very well until it becomes light and is double the original quantity. (as you do while making omelette)
Mix sugar and oil together, stirring hard till the mixture becomes light and fluffy.
Add the beaten egg to this mixture. Mix well to blend all ingredients thoroughly.
Now prepare a mixture of plain flour (maida) and baking powder and sieve it to avoid lumps.
Now gradually add this maida mixture, to the batter prepared by mixing sugar, oil and egg.
Note: If the mixture becomes thick, add a small amount of milk to make it smooth. Repeat the process of adding maida and then milk as required, till the batter is well blended (it should look fluffy/ soft).
Add vanilla essence to the batter and again blend well.
Baking the cake:
Use an aluminum baking tin - 6 inches in diameter, so that it can easily get into the pressure cooker.
Grease it on the insides & dust with maida, evenly.
Pour the mixture into the tin.
Heat the presure cooker on high heat for 2 minutes.
Caution: If baking tin comes into direct contact of the base of cooker, it can harm (overbake) the cake.
Remedy: Use a base cooker container - the one with big holes in it. You can put this on the base of the cooker & place the baking tin on it, inside the cooker. If you do not have the cooker container, this cake can still be made, but there is a big chance of getting its lower part overbaked.
Now put the cake tin (containing the cake batter), inside the cooker, on the base (holed) container. (Do not put water inside the pressure cooker).
Close the cooker lid and do not put the whistle on. Lower the flame from high to low after 2 minutes.
Let it cook for 40 minutes, then switch off the heat. Do not open the lid immediately.
After 10 minutes, open the lid to check whether the cake is done.
Pierce a dry skewer/knife/toothpick inside the centre of the cake.
If it comes out clean, without any cake batter on it, it means the cake is done.
Tip: For vegeterians: You can make the cake without egg. Just add 1/2 cup refined oil more. Make sure that you stir it pretty hard, till you find no air bubbles in the batter. For chocolate or other flavored cakes: Add 3/4 tbsp cocoa powder (or) a mix of 1/2 cup smashed dates/banana & 1/2 cup chopped walnuts (or) any mix of fruits & nuts of your choice for your desired flavour. For icing/decoration: Spoon whipped cream all over it and toss some dessictaed coconut on it (or) spoon some chocolate fudge icing on it & sprinkle choco-shavings or cocoa powder on the top. For black-forest variation: Cut the cake horizontally with a thread into 2 halves, spoon on some fruit juice (from the pitted cherries can) onto the base. Spoon on some jam/nutella/cream on its top and place some chopped pitted cheries on it. Place the top half of the cake on the base, repeat the juice-cream/nutella/jam-cherries steps & decorate as above. Enjoy!