Multnomah Falls Restaurant and Lounge
Multnomah Falls, Highway 84, east of Portland
Menu items are marked as gluten-free, including bread for sandwiches, etc. I ordered prime rib, which was excellent, and a side salad, which was better than average. The service was impeccable. The price for prime rib was $20. A side salad by itself costs $3.
You can see the falls from many of the tables.