Meanwhile, pour canned tomatoes into a bowl. Break the tomatoes up with your hand and discard any tough ends. Dice your pancetta and green onions and set aside.
In a large skillet over medium-high heat, cook pancetta until browned. Remove to a bowl. Add green onions and cook, stirring, until softened and starting to brown (there should be a bit of fat from the pancetta in the pan, but if not, add a bit of butter). Add the chili flakes and cook briefly. Add vodka and cook off until only a few Tablespoons of the vodka remains. Add the tomatoes. Reduce heat and simmer for 10-15 minutes. Add the butter, sugar and salt and pepper, to taste. Add the cream and stir to combine. Reduce heat to low until pasta is ready.
When pasta is cooked, drain and return to pot. Add sauce and cook, stirring, about 2 minutes. If necessary, add some pasta cooking liquid to loosen the sauce.