To make the porridge: Sift the flour and pour it into a bowl with some salt. Make a puddle in the middle and pour the egg, olive oil and pepper. Stir well until homogeneous and velvety. Let it rest for 1 hour.
Chop onions into rings, put them in ice water and leave for 30 minutes. Strain and dry well with kitchen paper.
Pour the sunflower oil into a deep frying pan and allow it to warm up. Slowly chop the onions, dip them in the porridge and then in the hot oil until they are a nice golden color (to perfectly fry and crisp the outside, do not sand them in the pan). When ready, take them out and leave them on a kitchen towel. They are served warm.