Preheat the oven to 375° and position a rack in the lower third of the oven. In a food processor, combine the flour, granulated sugar, baking powder, lemon zest and butter and pulse to blend. Add the whole egg and egg yolk and process until a soft dough forms. Turn the dough out onto a work surface and knead just until it comes together. Press the dough evenly over the bottom and up the side of a 10 1/2-inch fluted tart pan with a removable bottom.
Spread 1/4 cup of the preserves on the dough and arrange the peach wedges in concentric circles on top. Bake for 20 minutes, until the peaches are barely tender and the crust is still a bit pale. Brush the remaining 2 tablespoons of preserves over the peaches and bake for about 30 minutes longer, until the peaches are tender and the crust is golden. Immediately dust the tart with confectioners' sugar and let cool for at least 30 minutes before cutting into wedges and serving.