Heat a dry nonstick frying pan until hot, add the chillies and dry-fry for 1 minute on each side until lightly toasted. Transfer to a heatproof bowl, pour over boiling water to cover and leave to soak for 30 minutes until softened.
Add the whole spices to the pan and cook for 30 seconds until they emit an aroma. Tip into a pestle and mortar or spice grinder and grind until finely ground.
Remove the chillies from the soaking liquid, add to a mini processor or blender with the spices, oregano, vinegar, garlic, honey and oil and whizz to a smooth paste. Rub all over the pork in a shallow non-metallic dish, cover with clingfilm and leave to marinate in the refrigerator for 2 hours.
Wipe away any excess marinade from the pork, then place in a shallow baking tray and season. Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 25 minutes until just cooked through.
Meanwhile, make the salsa by mixing together all the ingredients in a bowl, then season.
Cut the pork into thick slices and serve with the salsa.