2 medium red bell peppers, four flat sides sliced off core, ribs and seeds discarded
2 medium yellow bell peppers, four flat sides sliced off core, ribs and seeds discarded
1 pound baby shells, or other short pasta
2 teaspoons olive oil
1 pound sweet Italian sausage (remove from casings, if any)
2 cups baby spinach
1 tablespoon butter, cut into small pieces
1/3 cup grated Parmesan cheese
Heat the broiler. Place the peppers, skin side up, on a foil-lined baking sheet; broil 4 inches from the heat until charred, 18 to 20 minutes. Transfer to a large bowl. Cover with plastic wrap; steam for 2 to 3 minutes. Using a paper towel, rub off the pepper skins, reserving any juices in the bowl. Set aside.
In a large pot of boiling salted water, cook the pasta according to package instructions. Drain, reserving 1/2 cup of the pasta water.
Meanwhile, heat the oil in a large skillet over medium heat. Cook the sausage, breaking it up with a wooden spoon, until browned, 7 to 10 minutes. Add the roasted peppers and spinach, cook until heated through.
Transfer sausage mixture to a large bowl; add the pasta, butter, and reserved pasta water if necessary. Finish with Parmesan and season with salt and pepper. Toss to combine.