Heat oven to 450 degrees F. Brush pork with olive oil, season with salt and pepper, and add to center of roasting pan. Arrange onion and potatoes around pork tenderloin in pan. Add beef broth and thyme.

Roast until pork registers 140 degrees F and vegetables are tender and golden brown, about 25 minutes. Remove from oven, and cut pork into 1/2-inch-thick slices. Arrange pork over roasted vegetables on serving platter, and pour any accumulated juices over top. Serve with garnish of fresh thyme.