Preheat oven to 375°.
Combine first 4 ingredients in a small bowl; rub pork with spice mixture. Refrigerate 30 minutes.
Heat a large nonstick skillet coated with cooking spray over medium-high heat; add pork. Cook 6 minutes; brown on all sides. Place on a broiler pan coated with cooking spray. Bake at 375° for 30 minutes or until thermometer registers 155°. Let stand 10 minutes before slicing.
While pork bakes, melt the butter in a medium saucepan over medium-high heat. Add the onion, and cook 10 minutes or until golden brown, stirring frequently. Add ginger, and cook 4 minutes. Stir in broth and syrup, scraping pan to loosen browned bits. Bring broth mixture to a boil; cook until reduced to 3/4 cup (about 10 minutes). Cut pork into 1/4-inch-thick slices; serve with sauce.