In a large saucepan, cook the pancetta over medium-low heat, stirring occasionally until browned and crisp. Transfer the pancetta to a small bowl and set aside. Add onions, garlic and hot pepper to the pan and cook until the onions are softened and browned, about 3 minutes. Add cream, sun-dried tomatoes and pancetta. Simmer until the cream thickens slightly, 3 minutes. Remove the garlic clove and remove the pan from heat.
Cook Spaghetti in a large pot of boiling salted water until al dente. Drain the pasta and reserve about 1 cup of the cooking water. Add the hot pasta directly to the saucepan along with the grated Parmigiano. Toss to coat; add the reserved pasta water as needed to obtain a creamy smooth sauce.