Use newly generated API Key from Powershell in Octopus Deploy - powershell

Question

I am generating a new API Key with the following Powershell script:
function CreateAPIKey{
Param(
$OctopusURL,
$APIKey,
$UserName,
$APIKeyPurpose,
$NewAPIKey
)
##PROCESS
$header = #{ "X-Octopus-ApiKey" = $APIKey }
$body = #{
Purpose = $APIKeyPurpose
} | ConvertTo-Json
#Getting all users to filter target user by name
$allUsers = (Invoke-WebRequest "$OctopusURL/api/users/all" -Headers $header -Method Get -UseBasicParsing).content | ConvertFrom-Json
#Getting user that owns API Key that will be deleted
$User = $allUsers | where{$_.username -eq $UserName}
#Creating API Key
$CreateAPIKeyResponse = (Invoke-WebRequest "$OctopusURL/api/users/$($User.id)/apikeys" -Method Post -Headers $header -Body $body -UseBasicParsing -Verbose).content | ConvertFrom-Json
#Printing new API Key
$NewAPIKey = $($CreateAPIKeyResponse.apikey)
Write-output "API Key created: $($CreateAPIKeyResponse.apikey)"
}
CreateAPIKey $OctopusURL $APIKey $UserName $APIKeyPurpose $NewAPIKey
The script works fine and creates a new api key when I run it from Octopus Deploy. I am then setting up project in Octopus where I want to send an email to myself with the user name and new API Key. I have setup variables where the Username is hardcoded and displays in the email fine. But I dont know what value to assign $NewAPIKey as seen below.
When I recieve the email all I get is the #{NewAPIKey} where the APIKey should be.