1) Preheat oven to 350 degrees F. Cook lentils according to package by simmering in boiling water. Be careful not to over-cook the lentils as they will just turn to mush.
2) Drizzle salmon with olive oil and season with salt and pepper. Add salmon fillet, skin-side up, to a hot, oven-safe skillet over high heat. Sear salmon for 3 minutes and flip.
3) After searing the fillets, turn them skin side down and add a small knob of butter to each fillet. Stick pan in the oven and finish cooking for 5-7 minutes. The total time will depend on thickness of the salmon.
4) For lentils add olive oil to a large pan over medium-high heat. Once hot, add onions, celery, and carrots. Cook until veggies are soft, about 5 minutes. Add garlic and season with salt and pepper.
5) Stir in cooked and drained lentils, capers, and fresh thyme. Stir to combine flavors.
6) Add butter and lemon juice to finish the lentils and season with salt and pepper.
7) Serve the seared salmon on a bed of lentils garnished with fresh lemon.