Soak the urad dal and rice in a bowl of water for 3 hours.
Transfer the dal and rice to a blender or food processor, season with salt, and process to make a stiff, smooth batter.
Add the remaining ingredients, except the oil, and mix well, then shape the batter into lemon-sized balls.
Heat enough oil for deep-frying in a kadhai or deep, heavy-based pan to 180°C / 350‘F, or until a cube of bread browns in 30 seconds, then reduce the heat to low.
Working in batches, deep-fry the Bonda for 3-4 minutes, or until golden brown and crisp. Remove with a slotted spoon and drain on kitchen paper (paper towels). Serve hot.