Generally, when blind-baking pastries, it is standard practice to use a circle of parchment filled with pie weights (or dried beans) to hold down the pastry as it bakes. That said, I don't usually use pie weights for this tart because it seems to bake up fine without them. If you'd like to use pie weights when you blind bake the tart shell, bake it for 8 minutes, and then remove the pie weights and bake an additional 5 minutes before moving on.