In order to build an electron desktop app, you need to make sure you have hosted your API to a live server. The live link to your API will be needed when you want to build the front end. You can watch this video here Publishing your Radsystems Project - Tutorials - Radsystems Forum.
What you want to do is similar to what was done in the video, the only difference is that you will not host the front-end.
From the video, in place of running the below command to generate the SPA frontend
quasar build
you will run this command below.
quasar build -m electron
You can read more here Electron Build Commands | Quasar Framework