Heat oil in large heavy pot over medium high heat until it shimmers. Add onion, garlic, chili pepper flakes and 1/2 teaspoon salt. Cook stirring occasionally until the onion turns a nice golden brown ~6-8 minutes.
Stir in tomatoes, tomato paste and pork. Let the mixture come to a simmer, while stirring, break up tomatoes. Continue to simmer over low heat until sauce has thickened. This will take approximately 25 minutes with fresh tomatoes and 15 minutes with canned tomatoes.
Season to taste with salt.
Cook the pasta according to directions. Drain well, toss with sauce and sprinkle with parmesan.
Garnish with parsley. Serve immediately. Have additional parmesan on table.