How to Make It
Cook the penne in a large pot of boiling salted water until al dente. Meanwhile, in a large bowl, toss the arugula with the parsley, basil, mint and scallions. Heat the olive oil in a small skillet. Add the garlic and cook over low heat until fragrant, about 1 minute.
Reserve 1/4 cup of the pasta cooking water. Drain the penne and add it to the bowl. Add the reserved pasta cooking water to the skillet and bring to a simmer. Remove the skillet from the heat, add the butter and let melt. Stir in the lemon juice and zest, then pour the sauce over the penne. Season with salt and pepper and toss well. Serve the pasta at once.