Hi,
Since you just deleted it yesterday, have you tried re-activating your Azure subscription, restoring your App Service Domain (must be in same resource group and same subscription), and then once that is complete, obtaining authCode?
Reactivate a disabled Azure subscription - subscription was canceled
https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/subscription-disabled#the-subscription-was-canceled
Restore App Service domains within 30 days
https://azure.github.io/AppService/2019/08/06/How-to-restore-soft-delete-App-Service-domains.html
Excerpt from above article:
If you deleted your App Service Domain resource within the past 30 days, you can easily restore it by purchasing it again with the same Domain Registration Subscription and resource group. Unlike trying to purchase the domain name from other subscriptions or resource groups, the validation will allow you to purchase the same domain name.
As mentioned above, you need to first create the resource group using exact same name as it was before and then attempt to restore your App Service Domain.
Obtaining authCode
To transfer to different registrar you will need authorization code. You may open Azure Cloud Shell and execute command similar to below from App Service team blog (replace subscription id, resource group, domain name):
Invoke-AzRestMethod -Path "/subscriptions/<SUBSCRIPTION-ID>/resourceGroups/<RESOURCE-GROUP-NAME>/providers/Microsoft.DomainRegistration/domains/<DOMAIN-NAME>/transferout?api-version=2021-02-01" -Method PUT
In the output from the command, you need authCode, which is what you will provide the new domain registrar when requesting transfer in.
After the domain transfer process has completed and you have access to it at new domain registrar then you can go ahead and cancel your subscription again.
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP