Unroll pie crust and place on parchment-lined baking sheet. Spread grape jam over the pie crust leaving a 1-inch border around the edges. Randomly place tablespoon-sized dollops of ricotta over the grape jam. Fold in the edges of pie crust over the filling.
In a small bowl, beat the egg and brush over pie crust. Randomly place the grapes flat side down onto the crust. Bake for 20 minutes until crust is golden and filling is puffed slightly. Remove to a wire rack, cool 10 minutes. When cool, dust with powdered sugar and cut into slices.