Penne with Tomato Prosciutto Sauce

• 2 Tbs. olive oil
• 1 large red onion, finely chopped (about 2 cups)
• 2 cloves garlic, minced
• 6 oz. thinly sliced fine-quality prosciutto, such as prosciutto di Parma, finely chopped and separated into pieces (1½ cups)
• 2 28 oz. cans Italian plum tomatoes in juice, drained, reserving juice, and finely chopped
• 1 tsp. sugar
• ¼ tsp salt
• ¼ tsp freshly ground black pepper
• 1 lb. penne rigate
• Parmigiano-Reggiano, shavings or finely grated to pass at the table

Heat oil in a wide heavy medium pot over medium-high heat until it shimmers, then saute onion until golden, about 10 minutes. Add garlic and saute until golden, about 1 minute. Add prosciutto and saute until golden, about 4 minutes. Add tomatoes with reserved juice, sugar, and ¼ 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 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 the sauce in a serving bowl and serve remaining sauce on the the side. Pass the cheese at the table.