Wash quinoa in water multiple times. Due to the natural coating called saponin, there will be foamy water when you start washing quinoa. So, wash thoroughly until the foam is gone and water runs clear.
Once you have washed it well, soak the quinoa in water for 30 minutes. (refer notes 1) In the meantime, grate cucumber along with the skin and keep it aside. (refer notes 2)
Drain the water and wash it once again. Drain the water and transfer the quinoa to a mixer jar. Add 1-2 teaspoons of water and not more than that. Blend it to a smooth thick paste. To ensure that the quinoa is thoroughly blended, we should blend it separately and then add the other ingredients
Now, add all other ingredients- grated cucumber, green chilies, coriander leaves, grated coconut, and whole cumin seeds. Blend it to a smooth paste without adding any water (refer notes 4). Since we have used cucumber, its water content will be sufficient to grind.
Once this is done, transfer the batter to a bowl/container. Add salt and mix well. The consistency should be like that of the usual dosa batter. If itis thick, add some water. I did not use any additional water except for 2 teaspoons while blending quinoa. The water quantity in cucumber was good enough.
Heat the tawa you use to make dosa. If it is a cast iron tawa, drizzle some oil and rub with onion, once it turns hot.
Pour a ladle full of batter onto the tawa, spread it uniformly. You can spread it as thin as you want or keep it thick, based on your taste (refer notes 4).
Drizzle some oil and cover a lid. Once you see that the dosa has turned brown on one side, flip it and cook the other side.
Continue doing the rest of the dosas. Serve hot with coconut chutney.