Place the thinly sliced onion in a bowl
with juice 1 lime, half the oregano and a
pinch each of salt and pepper. Set aside.
Dry-fry the whole garlic in a non-stick
pan until blackened on both sides, about
8 mins, then peel. Heat the grill. Arrange
the thickly sliced onion on a baking tray
with the tomatoes, cut-side up. Season
and grill until blackened, about 8 mins.
Tip into a bowl with the garlic, chipotle
paste, 1 tsp chilli powder, 1 tbsp sugar
and remaining lime juice. Season and
whizz in a blender until smooth. Gently
heat through in a pan.
Rub the pork with the remaining chilli
powder, oregano, sugar and seasoning.
Grill for 5 mins each side until cooked.
Serve sliced in warm tortillas with some
sauce, the pickled onions and coriander.