Heat olive oil in a large skillet over medium-high heat.

Add the onions and cook until golden, about 8 minutes.

Add the garlic and red pepper; cook for 15 seconds.

Stirring the pepperoni and marinara sauce; bring to a boil.

Reduce heat, simmer for 10 minutes.

Stir in the salt and pepper.

Toss the sauce with hot pasta and the chopped parsley in the serving bowl.

Garnish with parsley sprigs.