Peel, halve and slice the red onion into medium half moon pieces. Place the sliced red onion, beef stir-fry strips, 4 tbsp red wine vinegar, 1 tbsp sugar and ¼ tsp chilli flakes into a large, non-metallic bowl. Set aside for 15 mins.

Meanwhile, weigh out 45g kale (see the tip for what to do with the rest). Prepare the kale by removing and discarding any large stalks. Roughly chop the leaves down to 1½in pieces. In a large bowl, combine the kale with a pinch of salt and 3 tbsp extra virgin olive oil. Peel and grate ¼ of a garlic clove into the bowl. Grate in the zest from the lemon and squeeze in the juice from one half.

Heat a medium pan over a low heat. Add 1 tbsp olive oil, the red onion from the beef dish and a pinch of salt. Tip any excess vinegar from the beef into the onions using a slotted spoon to keep the beef in the bowl. Cover. Cook for 8-10 mins or till soft, vibrant pink but without caramelisation.

While the onions are cooking, drain the lentils into a sieve and rinse them well under cold running water.

Remove the onions from the pan and add them to the kale and lentils. Return the pan to a high heat. Rub the beef strips with 1 tbsp olive oil and a pinch of salt.

Add the beef to the hot pan. Cook, undisturbed, for 2-3 mins or till the edges have caramelised but each strip is still pink in the centre. It’s important to make sure the pan isn’t overcrowded, so cook in two batches if necessary and don’t be tempted to stir the meat too much.

Add the hot beef to the lentils and kale and combine with salad spoons. Divide between plates and finish with a few more chilli flakes to taste. Eat warm.