Using Tabular Cubes On-Prem with Azure Gateway

Hi everyone. I'm looking to setup a Power BI dashboard in the cloud with on-prem tabular model SSAS cubes as the data source. My understanding is this is possible using an Azure Analysis Services on-premises data gateway configured in Azure with an on-premises data gateway setup and registered. While setting up a mockup of this environment in DEV I ran into a challenge.

1. How does one get the Cloud SSAS instance talking to the on-prem tabular models?

1a. Can I simply use Power BI Desktop to open the on-prem tabular models then publish the PBIX to SSAS in Azure and Poof! it just works?

2. Or do I take the on-prem tabular models I already have and publish those to Azure Analysis Services and the refresh will go through the data gateway to on-prem SQL Server?

I created the sample AdventureWorks model in Azure Analysis Services and I see that I can open it in Power BI Desktop.  It doesn't seem to get data from anywhere, however.  I'm still working my way through all the Microsoft Docs.  Not afraid of reading if you know where to point me.

Thanks for taking the time to read my inquiry!