Hey there @lukep!
I’m not experience with Node.js but can you check and try if that’s it to get rid of the cookies once logging out?
Make sure to hit v2/logout endpoint. When you redirect the user to the /v2/logout endpoint, Auth0 will clear the session server-side and redirect to the returnTo URL.
Here’s more on logout:
This thread also might be helpful as it touches the same issue:
http://community.auth0.com/t/log-out-doesnt-work-and-automatically-sign-in/14826/12
Let me know down the road if you were able to solve the riddle!