If you were to find me in a restaurant in the early 2000s, chances are I would be eating seared tuna on a ‘bed’ of le Puy lentils. I couldn’t get enough of it.It seemed to be the height of sophistication and was pretty much the dish de nos jours, as it were. But, as fashions come and go, so did my taste for it. I got bored. I’ve not been eating so much tuna since then, save for the occasional one with salsa verde so I thought, as we are currently trying to eat a low-carb diet –as well as a sugar-free diet as much as possible– I’d revisit it.I replaced the lentils with a warm bean salad, cut through with leeks, red onion and lemon. Use a thick slice of tuna from nearer the tail, it makes the cooking easier as you can watch it colour from the side.Ingredients2 thick tuna steaks, about 170g each4tbsp sesame seedsSalt and pepper to seasonFor the beans400g mixed cooked beans such as borlotti, kidney and cannellini1 small leek, thinly slicedZest and juice of a lemonA small bunch of slim asparagus spears1 red onion, finely choppedA good handful of fresh parsleyOlive oilSalt and pepper to seasonMethodGently cook the leeks and red onions in some olive oil and season with a little salt and pepper. Add the beans once the leeks are soft and stir in the lemon zest. Warm through and taste. Stir in the parsley and add more olive oil and lemon juice if it needs it then put this in a bowl and set aside and keep at room temperature then cook the asparagus until tender in salted, boiling water just before you cook the tuna.To cook the perfect tuna steak, take it out of the fridge about 45 minutes before cooking. Coat the tuna in a little olive oil then season with plenty of salt and pepper. Roll it in the sesame seeds. Bring a griddle pan to smoking hot then cook the tuna for about a minute on each side. Leave to rest for a couple of minutes then serve with the beans and asparagus.