First of all, set your sauce simmering.
Gently heat your olive oil in a saucepan and add your chopped tomato.
Stir around for a few minutes and then add your garlic, chilli flakes and pinch of salt and pepper.
Once your tomato has really softened, add your tomato paste (salça) and a ladleful of water.
Stir and heat through until the salça has dissolved.
Ladle in more water and add your vinegar and stir gently.
Continue to add more water intermittently to keep your sauce at the thickness you'd like.
After around 30 minutes, remove your pan from the head and seal with a lid to keep warm.