Heat 2 tbsp oil in a deep pan over medium flame.
Add mustard seeds and let them splutter.
Add chopped ginger and sauté for a few seconds.
Stir in the chopped onion and a pinch of salt; cook until the onions turn translucent.
Toss in the curry leaves and optional green chilies for extra flavor.
Add jowar rava and roast on low heat for about 5 minutes.
Gradually pour in warm water and lemon juice.
Stir well and cook uncovered until the water is absorbed and the upma is fluffy.
Optionally garnish with coriander leaves.