Stone Fruit Custard Tart

Name: Stone Fruit Custard Tart
Ingredients: ½ cup (1 stick) unsalted butter; ½ cup (65 g) raw pistachios, divided; 1 large egg; ¼ cup (packed; 50 g) light brown sugar; 2 cups (250 g) all-purpose flour; 1 tsp. kosher salt; ¾ tsp. baking powder; 3 large eggs; ⅔ cup (packed; 133 g) light brown sugar; ¼ cup sour cream; 1 Tbsp. vanilla bean paste or vanilla extract; 1 tsp. ground cardamom; ¾ tsp. ground ginger; ¾ tsp.(packed) finely grated orange zest; ¾ tsp. kosher salt; 3 Tbsp (23 g) all-purpose flour; 2½–3 lb. stone fruit (such as peaches, nectarines, apricots, and plums; all about the same size), cut into sixths or eighths, depending on their size; 1 Tbsp. coarse sugar; Powdered sugar, whipped cream, or crème fraîche (for serving; optional); A 9-diameter springform pan