Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Toss the cauliflower florets, diced carrot, and cubed tofu with the olive oil, sea salt, and black pepper until evenly coated.
Spread the vegetables and tofu in a single layer on the baking sheet and roast for 20-25 minutes until the edges are golden brown.
While the vegetables roast, sauté the onion and garlic in a large pot with a splash of water over medium heat until softened and fragrant.
Stir in the dry red lentils, turmeric, and vegetable broth, then bring the mixture to a boil.
Reduce the heat to low, cover the pot, and simmer for 15 minutes until the lentils are tender and have broken down slightly.
Add the roasted vegetables, tofu, and nutritional yeast into the pot, stirring gently to combine the flavors.
Use an immersion blender to partially blend the soup until it reaches your desired consistency, leaving some chunks for a hearty texture.
Stir in the fresh lemon juice just before serving to brighten the earthy flavors of the roasted vegetables.