Mix the urad dal, matar dal, and fenugreek seeds. Wash thoroughly a few times and soak in a bowl for 4 hours.
Separately, wash the sona masoori rice and soak it in water for 4 hours.
Drain the water from the dal mixture, add 230 ml of filtered water, and blend it in a high-speed blender until smooth. Transfer the batter to a large glass mixing bowl (or ceramic bowl).
Drain the rice, add 150 ml of clean water, and blend it into a slightly coarse batter.
Pour the rice batter into the same glass bowl as the dal batter. Mix well, cover, and leave to ferment in a warm place for about 8 hours (or longer in colder conditions).
Once fermented, add the beetroot puree (blend cooked beetroot with water) and salt to the batter. Mix thoroughly until the batter is evenly pink.
Heat a non-stick pan over medium heat. Pour a ladle of batter onto the pan, spread it evenly, and cook on both sides until crisp.
Fill your dosa with your favorite fillings. I love having it with a potato filling or lentil curry.
