plone.app.caching doesnt seem to support archetype.fieldtraverser's ++atfield+FieldName urls. Here's a quick hack to make it cacheable.
Add this into your configure.zcml:
Thats it. It should be following the contentItem caching rule settings afterward.
Add this into your configure.zcml:
<configure
...
xmlns:cache="http://namespaces.zope.org/cache"
...
/>
...
<cache:ruleset
for="archetypes.fieldtraverser.fieldtraverser.FieldContentView"
ruleset="plone.content.itemView"
/>
...
</configure>
Thats it. It should be following the contentItem caching rule settings afterward.