Add a little olive oil to the water in the pot to keep the pasta from sticking, boil, then add pasta; let boil 7 minutes for regular spaghetti or a little longer for other shapes (or to the al dente instructions on the box). Drain and keep warm.
In the skillet, heat the 1/4 cup olive oil on low-medium setting; add chopped onions, chopped tomatoes, oregano, and minced hot peppers. Stir and let sauté until the onions and tomatoes release their liquid.
Add the butter or margarine to the skillet, stir until melted. Continue to sauté until everything is well-heated through. Add the thawed shrimp and turn the heat up to medium; sauté 3-4 more minutes (if you cook the shrimp too long, they will shrink and become tough).
Fork the pasta on a plate or into a bowl and ladle some of the shrimp mixture on top, and enjoy.