If you take the road out of Orvieto heading towards Viterbo and once you get through the s-bends there are four restaurants within about a mile of each other. All are good but this place is the best for food especially pasta dishes.
You may have to book.

Deliciously interesting pasta. I had the envelopes with bagna cauda which was easily the best pasta I have had in Italy this year. The outside eating area is pleasant.

we were on the way and were attracted by the name of the place Buon Respiro (the good breathing). so we tried...and we were amazed by the quality of the restaurant, good food, special dishes and nice atmosphere.

Small trattoria a few miles out of Orvieto on the Viterbo road. Place had been recommended and indeed the food was very good. Had two lunches here with extended family which included young children..not a good idea. Not sure owner too keen on kids ! He tut tutted at a fallen serviette and seemed generally unfriendly, particularly scowling at us on the second occasion.Why did we venture a second time ? Food just so good.....
However the service from the waiter was excellent and cost reasonable.
Mostly locals eating here so one knows food will be good.

My family visits Italy every summer and we make sure we eat at Trattoria del Conte every time we are near. Why? Because it is AMAZINGLY delicious food, located off the beaten path, with beautiful views, lots of locals and lovely owners. I love the quaint, outdoor area and the homemade, perfectly prepared food. You will only get what's available and fresh that day - nothing frozen and reheated at Del Conte. Don't miss the pasta with truffles or the Umbrichetti Amertriciana. The Ricotto Affogato was voted best dessert in ALL of Italy by my daughters. Honestly, it is simply worth the drive.