This stew could not be simpler. The meat and onions caramelise in the pan (because they’re not submerged in liquid), and the vinegar loses some of its astringency through evaporation.
The only issue is the oven temperature, which depends on how long you’ve got, how heavy your casserole is (they can take a good while to warm up), and how warm your oven is (your gas mark S may be very different from mine).
You could stir in black olives at the end. You might also want to include herbs such as thyme or rosemary.
2 or 3 slices of belly pork, cut into fork-sized pieces
2 red onions, roughly chopped
6 whole cloves of garlic
Mix all the ingredients in a heavy casserole, with seasoning to taste.
I cooked my stew for 30 minutes at gas mark 6/200C, stirred it, gave it a further 30 minutes at gas mark 4/180C, stirred it again, and gave it a further 60 minutes at gas mark S/130C.