For the red sauce: In a food processor, puree the tomatoes to a smooth, creamy consistency.
Add the olive oil to a large pan over medium heat. Add the onion and saute until soft but not browned, 5 to 6 minutes. Add the garlic and the red pepper flakes if using and cook for another 2 to 3 minutes.
Add the pureed tomatoes and season with salt and pepper. Reduce the heat to medium-low and simmer for about 30 minutes. Strive for balance in the consistency of the sauce; it should be fluid but shouldn't look overly wet. A few minutes before taking the sauce off the heat, add half the basil and season with salt and pepper. Add the remaining basil just before serving. (Yield: 3 cups)
For the uovo al pomodoro: Preheat the oven to 375 degrees F.
Add a few ladlefuls of red sauce to two oven-safe skillets. In each skillet, crack 2 eggs directly on top of the red sauce. Season with salt and pepper, and transfer to the oven until the whites are cooked completely but the yolks are still runny, 4 to 5 minutes.
Garnish with the chopped parsley, and serve hot with a slice of grilled Tuscan bread on the side.
For best results, this dish should be prepared in single-serving cotto or cast-iron pans.