At this point the bacon is almost to our liking, so we blot up most of the bacon fat with paper towels, leaving about a teaspoon of fat in the pan. We add the onions and lower the heat to medium-low. We cook and stir as the onions get translucent.
When the pasta water is boiling and the onions are cooking, we add salt and the pasta to the water. When the pasta is 3 minutes away from being al dente, we remove the bacon to a plate lined with paper towels to crisp. We add the peas to the cooked onions and add about 1/2 cup of the pasta water. We add some freshly ground black pepper and reduce the heat to low.
The bacon is not as crisp as we like it, so we cover them with another piece of paper towels and microwave them for 20 seconds. They are done, crisp but not blackened! We let cool a second and crumble.
When the pasta is done, we strain it in a colander. We put the pasta back in the pot and add the peas and onions. We stir and then serve with the crumbled bacon, Locatelli and some red pepper flakes.