Hi @dscull ,
The goal is to extract the id from XML, Right? Please try below expressions:
//XML:
<root>
<id>CTASK0257585</id>
<key>GUID_ID_HERE</key>
</root>
//Flow Actions and expressions:

//For id:
join(xpath(xml(outputs('Compose')),'//id/text()'),',')
//For key:
join(xpath(xml(outputs('Compose')),'//key/text()'),',')
//Output:

-------------------------------------------------------------------------------------------------------------------------
If your question got an answer, please click "Accept as Solution "✅, If you liked my answer, please hit the "thumbs-up" 👍button.
Thank you,
Harsh Deol