Tips to unmold a tart in a 2 piece tart pan: from "The Pie and Pastry Bible"
Generally it is best to leave the crust in the pan until it is filled and baked, or chilled, as the pan gives the crust support. When ready to unmold the tart, place it on top of a canister that is smaller than the opening of the tart pan rim.
A flaky crust unmolds easily, but a sweet cookie crust unmolds most neatly when heated slightly. Wet a towel with hot water and wring it out well. Apply it to the bottom and sides of the tart pan. Press firmly down on both sides of the tart ring. It should slip away easily. If not, apply more heat.
Slip a large pancake turner between the bottom crust and the pan and slide the tart onto a serving plate.