Preheat oven to 425°F.

Gently stir together pears, cranberries, cornstarch, vanilla and lemon zest in a large bowl; set aside.

Heat a 10-inch oven-safe skillet over medium heat; add sugar and lemon juice, and cook until sugar dissolves, stirring frequently. Increase heat to medium-high; bring to a boil and continue boiling, without stirring, 1 1/2 to 2 minutes or just until mixture begins to turn golden brown.

Immediately remove skillet from heat and stir in butter until melted. Carefully spoon fruit mixture evenly over caramelized sugar.

Unroll pie crust and place over the fruit mixture, tucking the edges around the fruit along the inside of the skillet; bake 25 to 30 minutes or until crust is golden brown. Let stand 10 minutes, then carefully invert onto a flat, rimmed plate. Serve warm or at room temperature.