This is a great make-ahead meal; undercook the pasta by a few minutes if you plan on saving the soup and reheating at a later time.
Heat the olive oil in a large pot or Dutch oven over medium heat. Add the pancetta, and cook until crisp, 5 to 7 minutes. Remove the pancetta with a slotted spoon and reserve on some paper towels. Add the garlic and onions, and sauté until translucent, about 5 minutes. Add the stock, beans, and tomatoes, and cook until heated through. Remove 2 cups of the beans and liquid and purée using an immersion blender or in a standing blender. Return the purée to the soup and cook to a slow boil.
Stir in the pasta and add the pancetta back to the soup. Cook until the pasta is al dente, about 9 minutes depending on the pasta variety.