Pasta Amatriciana with Arugula

Pasta Amatriciana with Arugula
(inspired by Hathor's foodblog on eGullet)
1/2 lb pasta
~8 oz thick cut bacon, diced (I didn't weigh it, so I'm not exactly sure how much I used, but it was three slices of the thickest sliced bacon I've ever seen!)
1 small onion, diced fine
2 garlic cloves, minced or pressed
pinch red pepper flakes
1 c crushed tomatoes
large handful arugula, coarsely chopped
pepper to taste

Bring a big pot of water to boil.

While the water is boiling, start browning your bacon. When it's brown and crispy, drain off as much excess fat as you desire. Add the onion and cook until it softens. Add the garlic and red pepper flakes and cook until aromatic - about 30 seconds or so. Add the tomatoes and turn the pan down to a simmer.

Once the water is ready, add your pasta and cook until *just* al dente, maybe even a little bit the not quite al dente. When finished, reserve 1 cup of the pasta cooking water before draining. Add the drained pasta back into the pan with the sauce, along with 1/2 cup of pasta water. Turn up the heat and cook until the water is absorbed and the pasta is done, adding additional pasta water if necessary.

Turn off the heat and stir in the arugula, just until wilted. Serve immediately.