It is quite a drive north from Ubud along Jalan Tirta Tawar to get to Warung Bintang Bali, but the drive is worth it. Keep a look out on the left for the flags after driving for about 10 minutes from Ubud.
The tuna steak comes highly recommended, though there are plenty of other good choices on their very reasonably priced menu.
Sit and enjoy the farming land views, and get there early while there is still light.