1 1/2 pounds asparagus, ends trimmed, stalks and tips cut into 1-inch segments
Kosher salt
1/4 pound bacon, finely sliced
8 scallions, finely sliced, whites and greens reserved separately
1 pound fettucine or other noodle-shaped pasta
1 tablespoon juice and 1 teaspoon zest from 1 lemon
1 jalapeño pepper, seeded and cored, finely minced
3 tablespoons unsalted butter
3 tablespoons finely minced fresh parsley leaves
Freshly ground black pepper
1/2 cup finely grated Parmigiano Reggiano or Pecorino Romano, plus more for garnish