Combine the saffron with 2 tbsp boiled water from the kettle and set aside to infuse. Rinse the spinach and leave to drain in a colander.

Heat the oil in a shallow, non-stick frying pan over a low-medium heat and fry the onions for about 15 mins, or until golden. Add the saffron water, cumin and 1/4 tsp freshly ground black pepper. Mix well. Remove the onions to a bowl and set aside.

Tip the spinach into the pan, cover and cook over a medium- low heat for 2-3 mins, stirring occasionally until wilted. When the spinach is dark green, add the onions back to the pan and stir into the spinach. Season to taste and spread out in an even layer, then make two gaps in the mixture.

Put the melted butter in the gaps, then tip in the egg whites. Cover and cook for 2 mins, or until the whites are set. Remove the lid, carefully slide the yolks over the set whites, cover again and leave for another 1-2 mins until the yolks are cooked to your liking. Serve with the lemon or lime for squeezing over and bread for dipping.