Heat oven to 425°F. Brush 17x11x1-inch pan with 1 teaspoon of the melted butter. Unroll pizza crust dough in pan; press dough to cover bottom and 1/2 inch up sides.
Place pan on lowest oven rack. Bake 6 to 10 minutes or until crust is lightly browned.
Meanwhile, in 10-inch skillet, cook remaining butter and onion over medium heat 3 to 5 minutes, stirring frequently, until onion is crisp-tender. Add pears and brown sugar; cook 10 to 15 minutes or until pears and onion are tender and browned, stirring occasionally. Remove from skillet.
To same skillet, add chicken, Alfredo sauce, creamed spinach, pesto, rosemary and oregano. Heat over medium heat just until warm. Spread onto baked crust; top with pear mixture. Sprinkle with cheese.
Bake on center rack of oven 7 to 12 minutes or until edges of crust are brown and cheese is melted.