1.  Put the onion, lemon zest, juice and 1 tbsp. olive oil into a bowl, add salt and pepper to taste, then leave to soak for five minutes until the onion has softened a little.

2. Pour the hot stock over the couscous in a large bowl, cover with cling and leave for ten minutes until the stock has been absorbed.

3.  Season the tuna steaks. brush with oil, then pat themustard powder over both sides.

4.  Once the couscous is ready, add the parsley and capers to the onions, stir well, then mix into the couscous with a fork.

5.  Heat a griddle pan and sear the tuna for one minute on each side until medium-rare or for longer if you prefer.

Serve the tuna with the couscous and lemon wedges on the side.

Ingredients:

4 x 170g / 6 oz. Tuna Steaks

1 Red Onion - finely sliced

Zest & juice of 1 lemon, plus wedges to serve

1 tbsp. olive oil, plus extra for brushing

400ml / 14 fi.oz. hot vegetable stock

250g / 9 oz. Couscous

2 tsp. English Mustard powder

Bunch of flat-leaf parsley - roughly chopped

2 tbsp. capers