Sweet Pastry Dough (for one crust, rolled into an 11-inch circle)
1 ¾ cup
(3 by 1 inch) lemon peel (no white pith)
vanilla bean (split lengthwise)
cardamom pods (crushed)
1 ½ lb
(about 10) firm-ripe apricots (halved lengthwise and pitted)
crème fraîche or sour cream
heavy (whipping) cream
pure almond extract
1/4 stick unsalted butter (preferably European plugrá, melted)
Position a rack in the center of the oven and preheat to 400 degrees F.
Carefully fit the pastry into a 9x1-inch tart pan with a removable bottom, folding the excess dough overhang inward to create a double thickness at the edge. Place the tart pan on a rimmed baking sheet. Prick the bottom and sides of the crust with a fork, about 20 times. Firmly press a 12-inch sheet of parchment paper or aluminum foil against the sides and bottom of the crust. Fill the shell with pie weights. Bake for 15 minutes, then remove the pie weights and parchment paper.
Reduce the oven temperature to 350 degrees F. Return the tart on the rimmed baking sheet to the oven and continue baking until the crust is just firm, about 10 minutes. Do not let the crust brown. Remove from the oven and let it cool completely.
While the crust is baking, combine 1 cup of the sugar, the water, lemon peel, vanilla bean, and cardamom pods in a large saucepan. Bring to a simmer over medium-high heat, stirring to dissolve the sugar. Reduce the heat to low and cook the syrup for 10 minutes to infuse the flavors. Add the apricot halves and simmer the fruit for 2 to 3 minutes. Do not overcook: the apricots should still hold their shape and the skins should be intact. Transfer the apricots with a slotted spoon to a platter and allow to cool. Reserve the cooking syrup in the pan. Scrape the seeds from the vanilla bean into the syrup; wash and dry the pod and reserve for another use, if desired.
Raise the oven temperature to 425 degrees F.
Arrange the apricot halves, cut side up, in concentric rings in the blind-baked crust. Overlap slightly if you have enough. Place the tart on a rimmed baking sheet.
In a medium-size bowl, whisk together the eggs, creme fraiche, heavy cream, and the remaining 3/4 cup of sugar. Add the melted butter and stir to blend. Pour the custard over the fruit; you may have slightly more than you need. Bake the tart until the custard begins to set and takes on a light golden color, 15 to 20 minutes. Lower the oven temperature to 350 degrees F and bake until the filling is firm, has puffed, and does not wiggle, 15 to 20 minutes more.
While the tart is baking, cook the poaching the syrup over medium-high heat until it reduces to a thick syrup and turns pale golden, 30 to 40 minutes. Keep the syrup warm.
Remove the baking sheet from the oven and let the tart cool completely. Just before serving, drizzle some of the syrupy glaze over the tart. Serve at room temperature. The tart can be refrigerated for up to 2 days, covered with plastic wrap. Allow to warm to room temperature before serving.