Peel the shrimps while keeping their tail on and de-vein them. Remove the heads from the shrimps and keep them aside. Put the shrimps in a bowl filled with half of the ouzo and allow to marinate for 30 minutes.
In a large pot add the shrimp heads, bring water to a boil on high heat adding a generous amount of salt. When it boils remove the shrimp heads and add the pasta, stirring occasionally so as not to stick and cook according to suggested time on the box of the pasta less 2 minutes. Reserve ¾ cup of cooking water.
In the meantime, in a large and deep sauté pan over medium heat pour the olive oil and when hot toss in the cherry tomatoes, onions and peppers. Sauté for 2-3 minutes and then add the cubed tomatoes. Season with the salt and pepper along with the chili flakes and the oregano, reduce the heat to low and allow for the sauce to thicken.
Add to the pan the shrimps with their ouzo marinate, increase the heat and cook for a total of 4 minutes stirring halfway through. Add the remaining ouzo and the parsley stir for a minute, turn off the heat and go back to the pasta.
Drain the pasta and return to the pan with the sauce and the shrimps. Stir for a minute so as the pasta absorbs the sauce and add some of the reserved water if needed.
Serve in a deep dish and drizzle some olive oil. Parmigiano Reggiano cheese on the side as not everybody enjoys fish pasta with cheese.