Heat the olive oil in a large soup pot over medium heat.
Add the diced onion, carrots, and celery to the pot and sauté for 5-7 minutes until the vegetables begin to soften.
Stir in the minced garlic, sea salt, black pepper, and dried thyme, cooking for another 60 seconds until fragrant.
Rinse the red lentils thoroughly and add them to the pot along with the cubed firm tofu and vegetable broth.
Bring the liquid to a gentle boil, then reduce the heat to low and cover the pot.
Simmer for 15-20 minutes, or until the lentils are tender and have thickened the soup.
Stir in the nutritional yeast and chopped kale, allowing the kale to wilt for 2 minutes in the residual heat.
Turn off the heat and stir in the fresh lemon juice to brighten the flavors before serving.