Heat the olive oil in a large pot over medium heat. Add the diced onion and sauté for about 5 minutes until softened.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the sliced mushrooms, diced carrot, and diced celery to the pot. Cook for about 7-10 minutes, stirring occasionally, until the mushrooms release their moisture and start to brown.
Sprinkle in the dried thyme, dried rosemary, salt, and black pepper. Stir to combine and cook for another minute.
Add the white beans, vegetable broth, and diced tomatoes (with juices) to the pot. Bring the mixture to a boil, then reduce the heat to low and let it simmer for 20 minutes.
Stir in the chopped kale and lemon juice, and cook for an additional 5 minutes until the kale is wilted and tender.
Taste and adjust seasoning if necessary before serving.