How to add and automatically validate a custom apex domain which is hosted on Azure DNS to an Azure Static Web App using Bicep?

Question

I currently have this on my Bicep template:

// Static Web App
resource staticWebApp 'Microsoft.Web/staticSites@2024-04-01' = {
  name: resourceName
  location: location
  tags: tags
  sku: {
    name: staticWebAppConfigs.home.skuName
    tier: staticWebAppConfigs.home.skuTier
  }
  properties: {
    stagingEnvironmentPolicy: staticWebAppConfigs.home.stagingEnvironmentPolicy
    allowConfigFileUpdates: staticWebAppConfigs.home.allowConfigFileUpdates
    enterpriseGradeCdnStatus: staticWebAppConfigs.home.enterpriseGradeCdnStatus
  }
}
// Create A record as an alias to the static web app resource
module aRecord './dns-record.bicep' = {
  name: 'deploy-a-record-${resourceName}'
  scope: resourceGroup(sharedResourceGroupName)
  params: {
    dnsZoneName: staticWebAppConfigs.home.dnsZone.zoneName
    recordName: '@'
    recordType: 'A'
    recordValue: ''
    isAlias: true
    targetResourceId: staticWebApp.id
  }
}
// Custom Domain resource - single domain
resource customDomain 'Microsoft.Web/staticSites/customDomains@2022-09-01' = {
  name: staticWebAppConfigs.home.customDomain
  parent: staticWebApp
  properties: {
    validationMethod: 'dns-txt-token'
  }
  dependsOn: [
    aRecord
  ]
}

But this causes my Bicep deployment stack to get stuck deploying the customDomain.

It's now been stuck on deploying that resource for 40 minutes.

If I access the static web app resource and visit the custom domains tab, I can see that the custom domain status is "Validating" and I can see the TXT record that needs to be added to the DNS zone.

I'm confused though because if I do this manually via the Azure Portal I can go to Custom domains > Add > Custom domain on Azure DNS then I select my DNS zone and leave the subdomain field blank and click add then it'll say "Validating" for a bit but it will ultimately add the TXT record to the DNS Zone automatically, without me doing anything else.

How do I specify that my custom domain is on Azure DNS when deploying the Microsoft.Web/staticSites/customDomains resource? It seems to think im using an external DNS and waiting for me to add the TXT record manually.