On a dry skillet, roast the rava, stirring constantly, until it turns just a couple of shades darker and smells fragrant. Always roast on medium to medium-low heat because you don't want to burn it, and don't leave the rava unattended on the stove. Once it's roasted, remove to a plate and set aside.
Heat the oil in the same skillet. Add the mustard and asafetida and wait for the mustard seeds to sputter.
Immediately add the curry leaves, green chillies, onions and spring onions. Saute until the onions are soft but not brown. Add the ginger and stir in.
Add the red bell peppers and turmeric and saute until the peppers are softened, about 2-3 minutes.
Now add the water and bring it to a boil. Add salt.
Turn the heat to low and have a ladle ready or a sturdy fork ready.
Slowly, pour the roasted rava into the skillet and immediately start mixing it in with the water. Work fast because you don't want dry lumps in your upma. You want to get everything mixed in fast so that every grain of the rava absorbs the water.
Turn off the heat and mix in the coriander leaves and coconut, if using. Serve in bowls with slices of lemon that you can spritz over the upma, and, if you desire, some coconut chutney