In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 3-4 minutes until it becomes translucent.
Stir in the minced garlic, diced carrot, and diced celery. Cook for an additional 5 minutes, stirring occasionally.
Pour in the vegetable broth and bring the mixture to a boil.
Once boiling, add the white beans, chopped kale, dried thyme, salt, and black pepper. Reduce the heat and let it simmer for about 15-20 minutes, or until the kale is tender.
Stir in the lemon juice just before serving.
Serve hot, garnished with grated Parmesan cheese if desired.