1. Heat the oven to 350 degrees . Line two cookie sheets with parchment paper. Place the raisins in a small bowl, cover them with water, and let them soak for 15 minutes.
2. In a large bowl, sift together the flour, sugar, salt, baking powder, cinnamon, and nutmeg, then stir them until they're evenly blended.
3. Set aside 3 tablespoons of water from the bowl of raisins, then drain the raisins, discarding the remaining water.
4. Whisk the egg in a medium bowl. Stir in the vanilla extract, melted butter, and reserved raisin water.
5. Make a well in the flour mixture, then pour in the egg mixture and blend well. Use a spatula to stir in the oats and the raisins. Note: The dough will be lumpy.
6. With a tablespoon or a cookie scoop (1 1/2 tablespoon size), place portions of the dough on the cookie sheets, then use a spatula to flatten them slightly.
7. Bake the cookies one pan at a time, rotating the pan halfway through, until they're golden brown, about 16 minutes. Let the cookies cool on the sheet for 3 to 4 minutes, then use a spatula to transfer them to a wire rack to cool completely.