Preheat your oven to 400°F and line a baking sheet with parchment paper.
Toss the sliced carrots and halved Brussels sprouts with 1 tsp of olive oil, half of the sea salt, and half of the black pepper.
Roast the vegetables for 20 minutes until they are tender and slightly caramelized.
While vegetables roast, heat the remaining 1 tsp of olive oil in a small pot over medium heat.
Add the finely diced onion and minced garlic to the pot, sautéing for 3 minutes until translucent and fragrant.
Stir in the dry black lentils, dried thyme, and vegetable broth; bring to a gentle boil.
Reduce heat to low, cover, and simmer the lentils for 25 minutes or until the liquid is absorbed and lentils are tender.
Season the chicken breast with the remaining salt and pepper, then pan-sear in a hot skillet for 5-6 minutes per side until fully cooked.
Slice the chicken breast and serve it over a bed of the braised lentils, topped with the roasted vegetables.