Step 1: Preheat your oven to 400°F (200°C). Roll out the pastry dough on a lightly floured surface and fit it into a 9-inch tart pan with a removable bottom. Trim the edges and prick the base with a fork.
Step 2: Line the pastry with parchment paper and fill with pie weights or dried beans. Blind bake for 12 minutes, then remove the weights and paper and bake for another 5 minutes until the bottom is set. Set aside to cool.
Step 3: In a large mixing bowl, combine the sliced pears, cranberries, granulated sugar, cornstarch, cinnamon, ginger, vanilla extract, and lemon juice. Toss gently to coat the fruit evenly.
Step 4: Arrange the pear slices in the par-baked tart shell, overlapping them in a circular pattern. Fill the gaps with the cranberries and any remaining juices from the bowl.
Step 5: Dot the top of the fruit with the small pieces of unsalted butter. Brush the edges of the pastry with a simple egg wash (1 egg beaten with 1 teaspoon of water).
Step 6: Place the tart on a baking sheet to catch any drips. Bake for 35-40 minutes, or until the fruit is tender and bubbling and the crust is a deep golden brown.
Step 7: Allow the tart to cool in the pan for at least 20 minutes before removing the outer ring. Serve warm or at room temperature.