Orange and saffron potatoes

1 onion, diced finely
2 tablespoons olive oil
100 mls sherry
½ teaspoon saffron threads
1 teaspoon sugar
Salt to taste
3-4 oranges, juiced
½ teaspoon sherry vinegar, or more to taste

Fry onion in olive oil and salt until softened. Cover with ½ cup water, and cook on high until water is evaporated. This is a quick way to fry onions.
Add sherry and cook on high until nearly evaporated.
Meanwhile grind saffron, salt and sugar in spice grinder. Alternatively, mix them together with a little boiling water.
Add to pan with orange juice, cover and simmer until cooked.
Check seasonings, and add more salt, sugar and vinegar to taste.
Serve warm or cold as a salad.