How do I get an Automation Action to apply a timestamp to a Date/Time field for the moment the Action occurs?

I have an Automation that is designed to create children records on a related table.  I'd like those children records to be timestamped with when they are created.  When I add an Action to the Automation for the Date/Time field [Timestamp], and put "Today()" in the field, it does not populate when the Automation is triggered.

I feel like this should be a pretty simple one, but I haven't been able to figure it out. Thanks!