Sheet Pan Panzanella with Squash and Prosciutto

Name: Sheet Pan Panzanella with Squash and Prosciutto
Ingredients: 1 medium acorn squash (about 14 ounces); 1 medium lemon; 2 large leeks; 5 tablespoons olive oil, divided; 1 teaspoon packed light brown sugar; 1 teaspoon kosher salt; 1/2 teaspoon freshly ground black pepper; 8 slices prosciutto (about 3 ounces); 1/2 medium loaf ciabatta bread or sourdough boule (about 8 ounces); 1 medium bunch flat-leaf kale (about 8 ounces); 1/4 medium head radicchio (about 3 ounces); 2 ounces Parmesan cheese