Pappardelle with Spring Vegetables

Name: Pappardelle with Spring Vegetables
Ingredients: Kosher salt; 12 ounces pappardelle pasta; 1 cup frozen petite green peas; 2 tablespoons unsalted butter; 1 bunch radishes (about 8), halved or quartered if large; 2 tablespoons chopped shallot; Pinch of red pepper flakes; 5 cups baby spinach (about 3 1/2 ounces); 1 cup chopped mixed fresh herbs (such as parsley and chives); 1 teaspoon grated lemon zest, plus the juice of 1/2 lemon; Freshly ground pepper; 1/2 cup part-skim ricotta cheese