Rinse and drain the cooked lentils if needed, and cut firm tofu into bite-sized cubes.
Dice the carrot, celery, and onion. Mince the garlic.
In a large pot, heat a splash of water or a light drizzle of olive oil over medium heat. Add the minced garlic and diced onion, and sauté until the onion becomes translucent.
Stir in the diced carrot and celery, and cook for a few minutes until slightly softened.
Add the cooked lentils, tofu cubes, diced tomatoes, and bay leaf to the pot.
Season with thyme, rosemary, black pepper, and a pinch of salt. Mix well.
Pour in a small amount of water (or vegetable broth for extra flavor) to create a light stew consistency. Bring the mixture to a simmer.
Let the stew simmer for about 15-20 minutes, allowing the flavors to meld and the vegetables to become tender.
During the last 5 minutes of cooking, stir in the spinach until just wilted.
Taste and adjust seasoning if needed. Remove the bay leaf before serving.
Serve hot and enjoy this nourishing and herb-infused lentil and vegetable stew.