Begin by bringing a large pot of salted water to a boil. Once boiling, add the spaghetti and cook according to package instructions until al dente. Drain the spaghetti using a colander and set aside.
In a large skillet, heat the olive oil over medium heat. Add the diced red onion and sauté until translucent, about 3-4 minutes. Next, add the green bell pepper and continue to cook for another 2-3 minutes.
Add the Dominican salami to the skillet, breaking it up with a wooden spoon. Cook until the salami is browned and crispy, which should take about 5 minutes.
Stir in the crushed garlic, pitted green olives, capers (if using), and diced plum tomatoes. Cook for an additional 2-3 minutes, allowing the tomatoes to soften.
Sprinkle the oregano over the mixture and pour in the tomato sauce. If you choose to use vinegar and evaporated milk, add them now as well. Stir everything together, and let it simmer for about 5 minutes.
Add the drained spaghetti to the skillet, tossing to combine well with the sauce and ingredients. Season with freshly cracked pepper to taste.
Serve your Dominican Spaghetti hot, topped with grated Parmesan cheese if desired. Enjoy your delicious creation with family and friends!