Preheat your oven to 325°F (160°C) (static setting, not convection) and bring the cookies back to room temperature while the oven is heating up.
Lightly roll your amaretti in another layer of powdered sugar. Place them on the prepared baking tray.
Bake in the oven for 20 to 25 minutes, possibly longer if the cookies are still cold. The cookies should not darken, but they will pick up color on the bottom, so be sure to check the bottoms before removing them from the oven.
If you make smaller cookies, 13 to 15 minutes should be sufficient (again, check for light golden color on bottoms).
The longer baked, the firmer they will get, so aim for a shorter baking time if you like them softer and vice versa if you want harder cookies.
Once baked and completely cooled, transfer the amaretti to tin boxes to store them. This helps prevent them from absorbing moisture and keeps them soft and delicious. Do not store while still warm.