Wash rice 2-3 times and then soak it for 1 hour.
Meanwhile, deseed the cucumber and cube the rest including the peel.
Grind the rice, grated coconut, cucumber, poha, and salt with a little bit of water into a thick batter.
Leave the batter overnight or for 6-8 hours. Let it ferment.
Heat a pan. Apply some oil to the surface. Pour a ladle of the batter on the hot pan. Spread it only a little( it has to be thick so it turns fluffy) and let it cook by placing a lid on it.
Lift the lid. Hole formation will be clearly visible on the dosa then flip it over to cook on the other side.
Serve it hot with chutney, pickles, dips etc