Heat oil in a cooker ,splutter mustard seeds,urad dal, and cashew nuts. Then add onion, ginger ,green chilli ,curry leaves and salt. saute till transparent. Then add vegetables and saute for few minutes. Then add hot water and boil. Then add rava and mix well. Allow to boil. Then check the salt. Add sugar and lemon juice. Now close the cooker and cook for 2 whistle in medium flame. After that allow to cool.Then open the cooker and with a fork puff up the upmavu. So the tasty and easy rava upma is ready to serve