Is there a way to **limit the creation of pages** (custom post type) to a **specific depth** - e.g. level 1 (where 0 = parent, 1 = child, 2 = grand-child, etc.)?

For example, let's create a 'Summer' recipe page (custom post type: Recipe) with a slug '/summer'. Let's now create a 'Pie' page (a child of 'Summer') with a slug '/summer/pie'. I want to prevent the user from creating a page which is a child of 'Pie' or of any other sub-page.

* example.com/summer -> GOOD
* example.com/summer/pie -> GOOD
* example.com/summer/pie/apple -> BAD
* example.com/summer/pie/blackberry -> BAD

Thanks.