Heat a saute pan on medium heat, add the olive oil then add the chopped onions. Add a pinch of salt to the onions and cook till nicely browned. About 5 minutes. Add the chopped spinach, chili flakes, salt and pepper. Give everything a good stir. Saute till the spinach is wilted and the mixture is dry. Taste to make sure the spinach is seasoned well, otherwise the quiche will be bland. Turn off the heat and let the mixture cool.