Puree the tomatoes to a smooth, creamy consistency in a food processor or with an immersion blender; set aside.
Heat the olive oil over medium-high heat in a large skillet. When hot, add the guanciale and saute 5 to 7 minutes, until golden brown.
Add the garlic and red pepper flakes and saute 1 minute. Add the pureed tomatoes, basil, and salt and pepper to taste. Reduce the heat to medium low and stir well. Cook, uncovered, 15 minutes, or until the sauce darkens and thickens. Toss with just-cooked pasta and serve with a sprinkling of parsley and cheese and a drizzle of olive oil.