Fill a large pot with water and bring it to a rolling boil. Season the water generously with salt, then add the spaghetti and cook as per packet instructions.
While the spaghetti is cooking, heat some olive oil in a frying pan and crack an egg into it, cooking it sunny-side up until the edges are crispy. Season the egg with salt and pepper and set it aside.
Once the spaghetti is cooked, reserve about 1/2 cup of the cooking water, drain the pasta and set it aside for later.
Stir in your tomato sauce. Cook this mixture for 2 to 3 minutes until the tomato sauce reduces slightly. Add the cooked spaghetti to the pot. Toss everything together over the heat for about a minute. If the sauce seems too thick, add some of the reserved pasta water to thin it out.
Season the spaghetti with salt and pepper. Plate the spaghetti, then place the fried egg on top. Add a sprinkle of chopped parsley and grated cheese if you wish.
Thinly sliced or diced onion and red capsicum would make a great addition to this pasta. Simply fry them until soft and stir in the pasta before serving.