Heat some olive oil in a medium frying pan over medium heat. Add the diced red onion and a small pinch of salt. Cook, stirring occasionally, for 5-7 minutes until the onion is soft, translucent, and beginning to turn golden at the edges. The slow cooking here draws out the natural sugars and builds the sweet, savoury foundation the whole dish rests on — don't rush it. In case it's needed, add a splash of water or broth to prevent burning.