PREHEAT oven to 350 ⁰F (180 ⁰C).
SPRINKLE chicken evenly on both sides with Cajun spice mix.
ADD canola oil in a large ovenproof sauté pan, over medium high heat and sear chicken on each side until spices turn dark but are not burnt.
FINISH chicken in the oven. Cook until chicken reaches an internal temperature of 165 ⁰F (74 ⁰C).
MEANWHILE, to prepare the lentils: In a large saucepan, heat canola oil. Sauté onions until golden. Add mushrooms and cook until golden as well, then add tomato paste with spice mix. Cook for 3 minutes.
MIX in stock, being sure to scrape the tasty bits off the pan with your wooden spoon. Add lentils and simmer for 5-10 minutes or until excess liquid is absorbed.
ADD butter, lemon juice, and parsley. Season with salt and pepper. Serve immediately with blackened chicken.