Non-traditional turkey tetrazzini

2 tbsp. butter
7 cups chicken broth
1 green bell pepper, cored, seeded, and finely chopped
1 large yellow onion, finely chopped
1 clove garlic, finely chopped
Salt and freshly ground black pepper
1 lb. dried spaghetti
1 lb. skinless boneless roasted turkey, torn into large chunks (about 3 cups)
2 cups frozen peas, thawed
1 cup ketchup
1 7-oz. can mushrooms, drained
¹⁄₄ cup finely chopped drained pimentos
3 cups (about ¹⁄₂ lb.) grated cheddar cheese
1. Preheat oven to 350°. Butter an 11" × 13" casserole dish
with 1 tbsp. of the butter. Combine broth, peppers, onions, garlic, and salt and pepper in a large pot and bring to a boil. Add spaghetti in broken pieces, reduce heat to medium, and boil gently, stirring often, until spaghetti is al dente, 12–14 minutes. Remove from heat, add remaining 1 tbsp. butter, turkey, peas, ketchup, mushrooms, pimentos, and salt and pepper to taste and fold together.
2. Transfer spaghetti mixture to buttered dish and cover with grated cheese. Bake until golden and bubbly, about 30 minutes.