Begin by bringing a large pot of salted water to a boil. Add in your asparagus and cook for about four minutes. Remove with some tongs, and place them in the ice water to prevent them from cooking any further, as well as retain their great green color.
To that same pot of boiling water, add in your capellini. Capellini is basically very thin Italian pasta. You will only cook this pasta for like 3-4 minutes as well as it is so thin. Once cooked, drain, and place inside your serving bowl.
Next get your dressing going. Roll a whole lemon on your counter to get the juices going, literally. Zest it, and slice it in half to gather all of the juice, of course being careful not to let any seeds get past you. So you have the zest and the juice sitting in a bowl. Toss in your garlic, chili flake, and olive oil, and mix well.
You are pretty much ready to go. Remove the asparagus from the ice water, and set aside. To your pasta, add the Pecorino Romano cheese, the asparagus, and the arugula. Add the dressing, and with some tongs, or a couple of forks, mix everything. You want to incorporate the dressing as best as you can, as well as the cheese.
Plate and serve.