Bring a large pot of water to a boil and add 1 tablespoon of the salt. Add the spaghetti and cook until slightly softer than al dente (about the package time minus 1–2 minutes). Drain and set aside.
While the pasta cooks, heat the olive oil in a large skillet or pot over medium heat.
Cut the salami into cubes and add to the hot oil. Cook, stirring, until the salami browns.
Reduce heat to medium-low and add the diced onion, diced bell pepper, olives, crushed garlic, and capers (if using). Cook, stirring, about 1 minute until the onion becomes translucent.
Add the cubed tomatoes and oregano, cover, and simmer 3–5 minutes until the tomatoes soften.
Stir in the tomato sauce. If using vinegar instead of milk, add the vinegar now. Mix well and heat through.
If using evaporated milk, add it now and stir to combine; do not let the mixture boil to avoid curdling.
Add the drained spaghetti to the sauce and toss until evenly coated. Season with the remaining salt (to taste) and black pepper.
Serve hot and garnish with grated Parmesan cheese if desired.