Step 1

Purée tomatoes with juices in a blender; set aside. Cook onion, guanciale, pancetta, oil, red pepper flakes, and 1/2 cup water in a large heavy pot over medium-high heat, stirring occasionally, until water is evaporated and fat begins to render, 8–10 minutes.

Step 2

Add tomato paste and cook, stirring often, until beginning to brown, about 2 minutes. Add wine and cook, stirring often, until reduced by half, 5–8 minutes.

Step 3

Add reserved tomato purée and bring to a boil. Cover pan partially with a lid, reduce heat, and simmer until meat is tender and flavors are melded, 40–45 minutes. Add sugar, if using; season with salt and pepper.

Step 4

When sauce is almost done, cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente; drain pasta.

Step 5

Add pasta to sauce and toss to coat. Serve topped with Pecorino.

Step 6

DO AHEAD: Sauce can be made 4 days ahead. Let cool, then chill until cold. Cover and keep chilled.