Master pages are automatically added to the bottom of the layers stack but there is a way to move them to the top on all pages in one operation
1. On any page that you have the master page applied, right-click the Master Page Layer in the Layers panel and select Edit Linked
2. With that Master page Layer still selected do Layer > Arrange > Move to Front (do not use the mouse to move the layers)
3. Click the Finish Button at the top of the screen
Now all pages that have that same Master page will have the Master page at the top of the stack
Note: The thumbnails in the Pages panel may not visually reflect that the Master page has been moved until you save, close and reopen the document
