1. In a large pot of heavily salted boiling water, cook the spaghetti to al dente according to the package directions. Reserve 1 cup of the pasta water (it comes in handy), then drain the pasta.
2. Meanwhile, in a large skillet, cook the pancetta over medium-high heat until crisped, 7 to 9 minutes. Add the olive oil, then add the garlic, red pepper flakes, and black pepper and cook until fragrant, about 1 minute.
3. Add the lemon juice to the skillet, then toss in the drained pasta and toss to coat. Add the Parm and toss, adding the pasta water, a couple of tablespoons at a time, just to help the cheese coat the pasta. Add the arugula and toss until it wilts, about 1 minute. Season to taste with additional salt, lots of black pepper, and red pepper flakes. Serve with more Parm.”
