At Doade, a few kilometres up the LU903 from the Río Sil towards Monforte de Lemos, the Algueira winery produces some of Ribeira Sacra's best wines and offers one-hour tours that include tastings (three wines) as well as an explanation of the challenges of wine-making in this difficult region with its steep slopes and varying microclimates. It's recommended to call ahead, especially if you want a tour in English.
You can also lunch at the restaurant here, O Castelo.