How to Make It
In a medium saucepan, cook the bacon until browned. Pour off and reserve all but 2 tablespoons of the fat from the pan. Add the onion, carrot, celery, and garlic. Cook over moderate heat, stirring frequently, until golden, about 5 minutes.
Add the lentils, broth, tomatoes, 1/2 teaspoon of the salt, the thyme, and bay leaf. Bring to a boil, reduce the heat, and simmer, covered, until the lentils are just tender, about 30 minutes. Discard the bay leaf and stir in 1/8 teaspoon of the pepper.
Heat the oven to 450°. Sprinkle the salmon with the remaining 1/2 teaspoon salt and 1/8 teaspoon pepper. In a large ovenproof nonstick frying pan, over moderately high heat, heat the reserved bacon fat, with enough oil to measure 2 tablespoons. Add the fish, skinned-side up, and cook until golden, about 2 minutes. Turn. Put the pan in the oven and continue cooking the salmon until just barely done (the fish should still be translucent in the center), about 3 minutes longer for a 1-inch-thick fillet. Put the lentils on plates and top with the salmon.