Thinly slice the Spanish onions and grate the potatoes and Parmesan cheese.

Heat the olive oil in a heavy-based pan.

Add the onions and cook over medium heat until tender.

Add the water and red wine and simmer for 20 minutes, or until the liquid has evaporated and the onions are a dark-reddish brown.

Combine the rosemary, potatoes, flour, yogurt, egg, and Parmesan cheese in a bowl.

Add the caramelized onions to the potato mixture and mix well.

Spread the mixture evenly into a well-greased 25cm ovenproof flan dish.

Bake at 200C (400F) for 35-40 minutes, or until golden brown.

Sprinkle with chopped Italian parsley, then cut into wedges and serve.