First of all roast the semolina till it will get pink colour and fragrant, once done keep aside.
Take green cardamom in mortar-pestle and powder them.
Now slice the cucumber and remove the seeds, if you are using regular cucumber then no need to remove the seeds, grate the cucumber and keep aside.
A lot of the cucumber juice will be collected in the bowl or in the plate, just add this to the batter.
In a bowl take roasted semolina, mix in the grated cucumber along with its juice, grated coconut, chopped cashews, powdered jaggery, cardamom powder and cumin powder.
Mix the batter very well without any lumps, the batter has a medium consistency and is neither too thick nor thin, depending on the consistency of the batter you can add a few tbsp of milk or coconut milk.
Now heat about 3 ½ cups water in idli steamer, grease the pan with coconut oil, pour the batter in the pan, place the pan in the steamer, cover the steamer with its lead.
Steam for 30-40 minutes until a knife inserted comes out clean, when the cucumber cake become warm or is cooked completely, then slice and serve.