Heat the olive oil in a large pot over medium heat. Add the onion, carrots, and celery with a pinch of salt. Cook, stirring occasionally, until softened but not browned, about 6 minutes.

Stir in the garlic, tomato paste, rosemary, and red pepper flakes if using. Cook 2 minutes, stirring, until the tomato paste darkens a shade and everything smells fragrant.

Pour in the diced tomatoes with their juices and the vegetable broth, scraping up any browned bits. Drop in the Parmesan rind, raise the heat to a lively simmer, then reduce to medium-low, partially cover, and cook 15 minutes so the flavors marry.

Stir in the drained cannellini beans. Mash about one-quarter of the beans directly against the side of the pot — this thickens the soup without cream. Add the chopped kale, pushing it under the surface; cook 3–4 minutes, until the kale is tender and wilted.

Fish out the Parmesan rind (it has given everything it has). Stir in the lemon juice and taste for salt and pepper. The broth should taste rich and balanced — add another pinch of salt before deciding it needs anything else.

Ladle into bowls, drizzle each with good olive oil, and shower with grated Parmesan. Serve with crusty bread for soaking up the broth.