Peel the onion and pierce it using the teo cloves. Boil the onion together with the lentils, the bay leaf, and the salt, in a small pan for 35 minutes. Drain the lentils, and discard the bay leaf and onion.
Add to the warm lentils 1/2 olive oil, vinegar, salt and oregano. Add the spring onions, the red pepper, celery, and mix well.
Heat the rest of the olive oil and sautee the trout for 2-3 minutes. Add the wine and simmer to reduce. Divide the lentils into four plates and top off with the trout. Sprinkle with pepper and serve.