Step 1

Peel the onions and finely chop them using a mandoline. Place the onion in a large bowl, sprinkle with salt and sugar and leave them to marinate for at least 2 hours or overnight.

Step 2

Place the onions (and the water they have exuded) in a pan, add the lard or oil or butter, cover with a lid and cook for 2 hours on a low heat, mixing them together and making sure they don't stick

Step 3

Cut the peeled tomatoes into large chunks and add the onion. Sprinkle with ground black pepper and continue cooking for another hour with the lid half off (using a wooden spoon to help keep the lid off)

Step 4

Once it's cooked, check the salt levels and serve with croutons or with flat bread.