Build your flavor base by heating olive oil in a large pot over medium heat. Add onion, carrots, and celery, and sauté for 5-7 minutes until vegetables begin to soften.
Add the aromatics – garlic, rosemary, and red pepper flakes. Cook for another 1-2 minutes until fragrant, being careful not to burn the garlic.
Incorporate the beans by adding the drained and rinsed cannellini beans to the pot. Stir to combine with the vegetables and herbs.
Pour in the broth and add the Parmesan rind if using. Bring the mixture to a simmer, then reduce heat to medium-low and cook for 15 minutes to allow flavors to develop.
Create texture variety by removing about 2 cups of the soup (avoiding the Parmesan rind) and blending until smooth using a blender or food processor. Return the pureed portion to the pot for a creamier base.
Add the kale to the pot and stir until it begins to wilt, about 2-3 minutes. The vibrant green leaves will soften but still maintain some texture.
Finish with brightness by stirring in the lemon juice and seasoning with salt and pepper to taste. Remove the Parmesan rind if used.
Serve hot with a drizzle of good olive oil and a sprinkle of grated Parmesan cheese if desired.