Lamb fajitas with chillied peppers, caramelised onion and tomato, avocado sour cream and Cheddar

Lamb fajitas with chillied peppers, caramelised onion and tomato, avocado sour cream and Cheddar
For 4

2 boneless lamb neck fillets
1 – 2 red chillies, thinly sliced (more or less to taste – or use a chilli sauce)
1 teaspoon fresh rosemary leaves (optional)
1 onion, peeled and thinly sliced
2 red peppers, halved, stem and seeds removed, thinly sliced
4 tomatoes, diced (or use canned chopped tomatoes)
1 avocado
1 lime (or ½ a lemon)
150ml sour cream
4 flour tortillas
100g Cheddar, coarsely grated
a handful of freshly picked herbs (mint, coriander, flat parsley)

Slice the lamb on an angle ½ cm thick and mix with half the chilli, the rosemary, 2 teaspoons vegetable oil and ¼ teaspoon salt
Leave to marinate for at least 10 minutes
In a fry-pan, caramelise the onions and peppers in a little vegetable oil then add the remaining chilli and tomatoes, and gently cook down to a dry stew
Meanwhile, mash the flesh of the avocado with the juice of the lime, ¼ teaspoon of finely grated zest and a little salt
Fold the sour cream in but only ripple it in, don’t mix it completely
Cook the lamb strips in a very hot griddle pan or fry pan but only cook to medium, take from the pan and rest for a few minutes in a warm place
Heat the tortillas up in the pan just to warm them through, then place on 4 plates and divide the onion pepper mix amongst them
Lay the lamb strips on top
Spoon on the avocado sour cream and sprinkle with the Cheddar and the fresh herbs