Cook thinly sliced onions in ample Spanish olive oil until tender. Do not brown. (A non-stick skillet may be the pan of choice in this country.). Remove with a slotted spoon and cook thinly sliced potatoes in the same oil. Sprinkle with salt and pepper. In a large bowl beat 6 eggs, add salt and the onions and potatoes. Mix lightly and pour into the skillet. Leave it alone over a slow flame. When the bottom is set, slide onto a pot lid of appropriate size, then flip the uncooked side back into the pan. A minute or two should do it. Slide onto a plate or board and cut into wedges.
Leave it on the bar long enough to pour a glass of Albariño.