Warm the pot. Set a heavy pot over medium heat. Add 2 tablespoons of olive oil and let it shimmer.
Sauté the base. Add onion, carrot, and celery with a pinch of salt. Cook 6–8 minutes, stirring, until the vegetables are soft and lightly golden.
Bloom the flavor. Stir in garlic and a pinch of red pepper flakes.
Cook 30 seconds until fragrant. Add tomato paste and cook 1–2 minutes to caramelize it slightly.
Add herbs and broth. Drop in rosemary and bay leaf. Pour in the broth and stir, scraping the bottom of the pot.
Beans two ways. Add 1 can of beans directly.
Mash half of the second can with a fork and add it in too. This gives the soup body without cream.
Simmer gently. If you have a Parmesan rind, add it now. Bring to a gentle simmer and cook 12–15 minutes so the flavors come together.
Add the kale. Stir in the chopped kale.
Simmer another 5–7 minutes, until tender but still bright. Remove the rosemary, bay leaf, and Parmesan rind.
Brighten and season. Add the zest of half a lemon and a squeeze of juice. Taste and season with salt and black pepper.
Adjust the heat with more red pepper if you like.
Serve. Ladle into bowls. Finish with a drizzle of olive oil and a shower of Parmesan if desired. Add crusty bread on the side.