To make the salsa, put the coriander (including the stalks) into the bowl of a food processor, along with the remaining ingredients. Whizz to a rough paste, then transfer to a serving bowl.
Rub the squash and red onion with some of the olive oil, sprinkle with a little of the cumin and season well. Heat a griddle pan (or the grill) until really hot and cook the squash for 5 minutes. Add the onion, toss around the pan and cook for a further 5-7 minutes until the vegetables are soft and lightly charred all over. Set aside and keep warm.
Rub the remaining oil and cumin into the pork and season. Cook the steaks for 3-5 minutes on each side. When done, cut into slices. Warm the tortillas in the oven or microwave then pile them with the vegetables and pork. Top with a little salsa and soured cream or yogurt, to serve.
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For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.