Heat oven to 425° F.
In a large bowl, combine the flour, ginger, nutmeg, and 3/4 cup of the sugar. Add the peaches and toss.
On a lightly floured surface, roll the dough into a 12-inch circle. Transfer to a baking sheet lined with aluminum foil. Arrange the peaches in the center of the dough. Fold the outer edge of the dough over the peaches, allowing it to fall into pleats, leaving the center of the tart uncovered. Lightly brush the dough with water and sprinkle with the remaining sugar. Bake until golden, 15 to 20 minutes. Reduce oven to 350° F and bake until the juices bubble and thicken, about 30 minutes more. Let cool for at least 20 minutes before slicing.