Dal bati churma is the dish that defines Rajasthani cooking — three components served together: dal (five-lentil soup), bati (hard wheat dumplings baked in an outdoor fire or oven), and churma (sweetened coarsely ground wheat mixed with jaggery and ghee). It is rich, filling, and completely different from the North Indian restaurant food most visitors know.
In Jaipur, the best way to eat it is at the small dhabas (roadside eateries) in the old city and along the lanes around Johari Bazaar. Annapurna on MI Road is a well-regarded spot that serves it formally; Rawat Misthan Bhandar (near the main bus stand) is famous for its pyaaz kachori (fried onion pastry) and also does a good dal bati. Both are inexpensive and busy with local customers.
The authentic version is cooked over a charcoal fire, which gives the bati a charred exterior and a soft, wheaty interior that's scooped out and dunked in the dal. Ask for it "traditional" style if you want the campfire-baked version rather than the oven-baked one now common in tourist restaurants.