A mustard vinaigrette gives this Mediterranean-inspired dish its tangy flavor. Drizzle some over a leafy-green salad, and serve it on the side.
Heat broiler. Combine lentils and 2 1/2 cups water in a medium saucepan. Bring to a boil; reduce heat, and simmer, covered, 5 minutes. Add onion and celery; cover, and continue cooking until lentils and vegetables are just tender, 15 to 25 minutes more. Drain, reserving cooking liquid. Transfer lentils and vegetables to a medium bowl.
In a bowl, whisk 2 tablespoons reserved cooking liquid with vinegar, oil, mustard, garlic, and parsley; season with salt and pepper. Toss half the dressing with the lentil mixture.
Meanwhile, season salmon with salt and pepper. Coat a baking sheet with cooking spray. Arrange salmon on sheet; broil until opaque throughout, 8 to 10 minutes. Spoon lentils onto plates; top with salmon, flaking it into large pieces, if desired. Drizzle with remaining dressing.
The cooking time for lentils can vary widely depending on their age. Older lentils require more time. For the best results, we recommend buying a fresh, new bag.
Chopped celery leaves add wonderful flavor to the lentils. Use them in place of or in addition to the parsley.