Place the lentils in a bowl and cover with boiling water. Set aside for 15 minutes then drain.
Heat oil in a saute pan. Add the onions, leeks, thyme, salt and pepper. Cook over medium heat for 10 minutes (until the onions are translucent). Add the Garlic and cook for 2 more minutes. Add the drained lentils, celery, carrots, chicken stock and tomato paste. Cover and simmer on low heat for 20 minutes. Add the vinegar and season to taste.
Salmon
Preheat the oven to 450
Heat an oven proof saute pan over high heat for 4 minutes. Rub both side of the Salmon fillets with oilve oil and season the tops liberally with salt and pepper
When the pan is very hot place the salmon, seasoned side down, and cook over medium heat WITHOUT moving them for 2 minutes. Turn the fillets and move the pan from the stove to the oven for 5-7 minutes
Spoon a mound of lentils onto a plate and top with a Salmon fillet.