[New Daddy]

I'm using my DD-WRT router as an access point.
But I'd like it to diver all traffic through a VPN gateway too.

So I've enabled DNSMasq under Services >> Services, and added "dhcp-option=tag:br0,3,192.168.0.61" which is my Raspberry Pi DNS gateway under Additional DNSMasq Options, but the traffic doesn't seem to be going through the DNS Gateway.

What next?

[egc]

It is always helpful if you state router model and build number and how you setup e.g. what wiki you used.

To get the best out of DDWRT and the forum read the forum guidelines with helpful pointers:
https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087

You mention setting up as an access point do you mean following this wiki:
https://wiki.dd-wrt.com/wiki/index.php/Wireless_access_point ?

If so then it acts as a switch and you have to set the DNS on your primary router (exceptions are unbridged interfaces those will use the DNS of the WAP).