Preheat the oven to 200°C conventional oven/ 180°C fan-forced (400° Fahrenheit/Gas 6).
To make the lentils, you will need to start by making the ‘soffritto’ (sautéed base flavouring). Heat half of the olive oil in a heavy-based stockpot over medium heat. Add the onion and cook for 2 minutes. Add the carrot, celery, and bay leaves then cook, stirring, for a few minutes until the onion is soft.
Stir in the lentils, then pour vegetable stock into the stockpot. Bring to the boil, then reduce heat to low. Cover and leave to simmer for 40 minutes or until the stock has been absorbed and the lentils are tender but still holding their shape. If the lentils are not tender, add more vegetable stock and cook until the stock has been absorbed and the lentils are tender to eat. Discard the bay leaves. Stir in the freshly chopped rosemary (or thyme).
Meanwhile season the Salmon fillets with sea salt and freshly ground black pepper. Rub the remaining olive oil and seasoning into the salmon. Heat an ovenproof frying pan over medium heat. Add the salmon to the frying pan (if using fillet with skin on, place salmon skin side down). Cook for 1 minute on each side. Transfer the frying pan to the oven. Cook for 3-5 minutes or until cooked to your liking.
To serve, place a ladle of lentils on each serving plate. Top with the Salmon fillet – buon appetito.