In a large pot of boiling, salted water, cook the pasta until al dente; drain and set aside.
In the same pot, melt the butter over medium heat. Add the onion and garlic and cook, stirring occasionally, until tender, about 6 minutes. Add the cream and simmer, stirring occasionally, until reduced by half, about 5 minutes. Add the reserved pasta, the tomatoes and beans and cook until heated through, about 5 minutes. Toss with the 1/2 cup parmesan and chives, then season to taste with salt and pepper. Pass more parmesan at the table.