Heat the oven to 400°F. Place the pie crust on a baking sheet. Roll the edges inward to form a rim. Arrange the pear slices in an overlapping circle. Chill until firm. Sprinkle over the sugar. Bake until the crust is golden brown and the pears are tender, about 20 minutes. Remove the baking sheet to a rack to cool and while the tart is still warm, brush with the warmed apple jelly. Let cool slightly then using a serrated knife, slice into wedges and serve.