Preheat oven to 180C. Wrap each beetroot in foil and roast for an hour until soft in the centre. When cool enough to handle,cut into 1-centimetre dice and mix with thyme and 100 millilitres olive oil.
Sweat onion,carrot,celery,garlic and bay leaves in a little olive oil until soft.
Add lentils,cover with cold water then bring to a simmer and cook until soft,but not mushy. Drain lentils and place in a bowl,add sherry vinegar and 30 millilitres olive oil and toss well.
Heat grill pan and start cooking the salmon skin side down to crisp it. After about 10 minutes,turn salmon and cook for about 5 minutes then leave in a warm place until needed.
Mix lentils,beetroot,mint and parsley. Mix mustard,lemon juice and remaining 100 millilitres olive oil for the dressing. Cut apples into matchsticks.
Add dressing to lentil salad,divide between eight plates,top with some apple sticks and finish with a piece of salmon. Drizzle with extra virgin olive oil and a squeeze of lemon.