Preheat oven to 400ºF.
Lightly dust a work surface with flour and lay out one pie dough round. It needs to be about the thickness of a nickel, so you may need to roll it out a bit to make it thinner. Place dough on a baking sheet.
In a large bowl, toss sliced pears with sugar and dump them into the center on the pie dough round. Leave about 1 to 2 inches of uncovered crust around the entire edge.
Fold that edge up so it encases the sides of the pears, brush with egg wash, then sprinkle crust edges with a little more sugar. Dot the top of the pears with 2 tablespoons butter. Bake until golden brown and the pears are cooked through, about 30 minutes.
Serve a slice of pear tart with vanilla ice cream.