Heat olive oil in large sauté pan over medium heat. Add onion and sauté until it is translucent and slightly golden, about 4 minutes. If you’re using garlic instead of onion, sauté it for 1 minute. If you want this to be spicy, add the red pepper flakes and sauté for 1 more minute. Add tomatoes. If whole, crushed them with the back of a spoon. Cook til mixture is fairly thick, about 20 minutes. Then season it with salt and pepper. Taste tomato sauce and if you think you’d like it to be a little sweeter, add the sugar. Stir in the basil leaves. Make six depressions in the tomato sauce with the back of a large spoon and break 1 egg into each depression. Baste eggs with a little tomato sauce, over the pan and cook over medium heat to pack the eggs, about 4 minutes.Carefully divide eggs and sauce among 3 or 4 bowls. Top with grated Parmesan if desired. The original recipe didn’t call for cheese, but it’s a nice addition. Serve with thick slices of bread.