bring port to a boil in a small saucepan over medium-high heat; cook 10 minutes or until reduced to 2 tablespoons. stir in cherry preserves; cook 45 seconds. remove pan from heat; stir in chopped thyme.
combine garlic powder, salt, and pepper in a small bowl. rub spice mixture evenly over pork. heat a large skillet over medium-high heat. add oil; swirl to coat. add pork to pan; cook 8 minutes, turning to brown on all sides.
place pork on a jelly-roll pan coated with cooking spray. roast at 425° for 20 minutes. brush pork with half of port mixture; roast at 425° for 5 minutes or until a thermometer registers 135°. 