Bring a large pot of water to a boil over high heat, then add a small handful of salt. Add the pasta and cook until al dente. Drain the pasta.
Meanwhile, heat the oil in a large saucepan or very deep skillet over medium heat. (Alternatively, cook the pasta and then wipe out the pot before proceeding.) Add the onions and garlic and cook, stirring occasionally, until softened, 5 to 7 minutes.
Add the kale, rosemary and crushed red pepper. Cook until the kale is just starting to wilt, about 3 minutes. Add the stock and bring to a simmer over high heat. Add the pasta, beans and tuna and simmer over low heat until hot, about 1 minute. Season with salt and pepper. Ladle into shallow bowls and top with grated Parmesan. Serve with crusty bread.