Place the peeled shrimp in a colander and rinse well. Remove and discard any pieces of the shrimp shell or any impurities. Hold aside.
Bring a pot of water to a rolling boil.
In a sauté pan, gently heat about half of the olive oil and add the finely chopped onion. Add a touch—about two teaspoons—of water. Cook the onion for approximately 15minutes, until light brown in color.
Crush the garlic cloves with the back of a knife or with the palm of your hand and roughly cut them in half. Add to the onions and stir the ingredients together. Let cook until the garlic is soft, making sure the cloves do not turn dark brown in color.
Roughly chop the tomatoes and add them to the pan along with a pinch of sugar and approximately 1 cup of water. (If using canned tomatoes in sauce, add the sauce to the pan as well. If using fresh tomatoes, after discarding the skin and seeds, add the tomato liquid to the sauce). Cook over high heat, stirring often, until the sauce has reduced by more than half.
Add the chopped parsley and the white wine and reduce slightly.
Add the peeled shrimp, the remaining olive oil, the salt and crushed pepper to taste. Stir all the ingredients together. The shrimp will release their liquid into the sauce. Cook until the sauce is reduced, doesn’t appear watery and coats the back of a metal spoon. Depending on the type and size of the shrimp, this process will take about 10 minutes.
While the shrimp are cooking, add salt to a large pot of boiling water. Add the pasta, stir so the strands don’t stick to one another, and cook until it is slightly underdone (less than al dente). When straining the pasta, reserve some of the pasta cooking water on the side.
Add the spaghetti to the sauce and stir constantly. Let cook until the pasta is al dente or until it reaches your desired consistently. It is important that the pasta sufficiently absorbs the sauce. If necessary, add a touch of the pasta water and additional olive oil.
Serve while hot.