It might be open on Sundays, but check in advance for wine tastings at La Comunale di La Morra. It’s the town hall and has a section selling/tasting plenty of wines by pretty much all the producers based in La Morra.
We were there 2 years ago, but on a Monday.
Sunday lunch may be a difficult time for many.
The listing on the langheroero.it site used to give opening hours during which each winery would take appointments. It wasn’t always accurate, but would be my starting point for a winery that might take a visit.
Alternatively, why not commit to a proper sunday lunch with wine to accompany the meal?
p.s. the cantina communale in Castiglione Falletto seemed very nice, despite us visiting in the middle of a power cut! Might be a nice option to fill the time out if required. However if you have longer, then even a short walk in the vines is very enjoyable.
RE: Restaurants
Nice list, my one trip to Piemonte, I ate at Il Centro, it was awesome (finding the entrance was a bit weird - front door locked?), I hear it recommended all over the place. I also hear La Ciau recommended a lot as well (didn’t have time to eat here, a must for my next time!), if you go there, get a tour of their cellar!
For more ideas on restaurants, I found a Chowhound thread (with link a to another post as well): Chowhound
Since a lot of restaurants aren’t that great at English, and the timezone is quite a bit off from me, we emailed our hotel to help make the reservations for us ahead of time.
La Ciau Tornavento in Treiso seems to divide opinion, from “the best” to “pretty poor, especially for the money”. It’s the one place in Treiso we didn’t go to, but the other three are all good in their different ways, so well worth making Treiso a destination and following your mood. La Ciau is definitely the place to go to if you really want to indulge yourself with wine.
I’ll throw in my enthusiastic +1 for Il Centro in Priocca. Excellent old-school cooking, exceptional family-style professional service that’s very cordial and friendly, and a very nice basement cellar to visit for some Nebbiolo gems. During dinner, 2 years ago, we had a 1990 Produttori Paje that’s been in the cellar since release … at Euro 80-90 iirc.