Two farms, both about 92 km from Cape Town, further up the Hemel-en-Aarde road than the valley ward. Alheit Vineyards and Restless River. That is the whole list.
Restless River asks you to book ahead. Neither farm publishes Sunday hours, so this is a poor place to arrive on a whim after the Hermanus cellars. Make the appointment, then drive up.
If you want a Sunday lunch and a published open door, stay in the Hemel-en-Aarde Valley ward. Whalehaven, La Vierge and Spookfontein all publish Sunday opening, and they sit closer to town on the same road.