A lovely savory pasta dish with ham. Use as a first course or main dish. Make the sauce in the morning to allow it to sit for 8 hours. It truly does need to blend the flavors. Prep time does not include 8 hours sitting time.
Heat oil in a wide heavy medium pot over medium-high heat until it shimmers, then sauté onion until golden, about 10 minutes. Add garlic and sauté until golden, about 1 minute. Add prosciutto and sauté until golden, about 4 minutes.
Add tomatoes with reserved juice, sugar, and 1/4 teaspoon each of salt and pepper and simmer, uncovered, stirring occasionally, until thickened, 45 minutes to 1 hour. Cool, uncovered, then chill, covered, at least 8 hours (to allow flavors to develop).
Cook penne in a pasta pot of boiling salted water (3 tablespoons salt for 6 quarts water) until al dente. Drain well.
While pasta cooks, reheat sauce over medium heat.
Toss pasta with some of sauce in a serving bowl and serve remaining sauce on the side.