Boil the spaghetti in enough water to cover them (about 2 liters) until slightly softer than al dente, having added 1 tablespoon of salt to the boiling water
While the spaghetti is boiling, heat oil in a large skillet or pot over medium heat. Cut the salami into cubes. Cook and stir the salami until it browns.
Add tomatoes and oregano, simmer covered until the tomatoes are cooked through (3-5 mins). Stir in tomato sauce and vinegar (do not add vinegar if you'll use milk). Stir to mix.
Add milk and the boiled spaghetti and mix well. Stir until the milk is mixed through, but do not let it boil or the milk will curdle. Season it with black pepper and salt to taste.\