Bring a large pot of well salted water to the boil and throw in the pasta. Cook until al dente.
In the meantime, in a large skillet or wok, sauté the garlic gently in abundant olive oil and along with the peperoncino if you like things spicy. When the garlic just begins to brown around the edges, discard it along with the hot pepper if using.
Add the tomatoes to the pan and let them sauté until they just begin to wilt, seasoning with salt. If your pasta isn't done yet, turn off the heat. (If you prefer more of a sauce, you can let them melt a bit more.)
When the pasta is done, drain and add to the pan, along with the arugula. (At this point you can also add the grated cheese if using.) Toss over lively heat for a few moments until the pasta and its sauce are well mixed and any excess liquid has cooked off.
Serve right away, topped with a drizzle of olive oil and, if you like, with additional grated cheese on the side for those who want it.