Heat the olive oil in a medium saucepan on medium heat
Saute the pancetta until crispy (skip this step if making it vegan)
Using a slotted spoon, take out the pancetta when finished cooking
Saute the onions in the saucepan in the leftover olive oil/pancetta fat until translucent. About 5-8 minutes
Next, saute the garlic and red pepper flakes in with the onions for about 1-2 minutes
Then pour the San Marzano tomato puree over the onion mixture in the saucepan
Salt and pepper the sauce to your liking
Let simmer for around 30 minutes
While the sauce is simmering, prepare your spaghetti squash, parsley, and Pecorino Romano cheese