Combine the flour, baking powder, nutmeg, cinnamon, and salt in a bowl. In another bowl, beat the eggs until light and frothy. Add the sugar and whisk to dissolve. Add the butter and vanilla and continue to whisk for 2 to 3 minutes. Add the flour mixture, about 1 cup at a time, blending together until a stiff dough forms. Lightly flour a work surface and sprinkle the dough with a little flour. Pat the dough into a large rectangle, about 1/8-inch thick. Using a pastry wheel or a sharp knife, cut out about 12 diamond-shaped pieces. Make a slit lengthwise through the center of each diamond. Preheat the fryer. Deep-fry the diamonds, 2 to 3 at a time, turning them around with a slotted spoon, until they are golden brown and crispy, about 4 minutes. Drain on paper towels. Dust with confectioners' sugar and serve immediately.