Yep! tuns would be the service you want since it can support forwarding arbitrary backends: https://pico.sh/tuns#custom-domains

Thanks. Let me know if I misunderstood, but it seems that this is redirecting my custom domain customdomain.example.com to tuns.sh

customdomain.example.com. 300 IN CNAME tuns.sh.

_sish.customdomain.example.com 300 IN TXT "SHA256:mVPw"

What I want to do is:

1- to create a custom domain ON tuns.sh (or another Pico service)

2- redirect this custom domain to another DNS (such as a Load Balancer, an API Gateway, etc.)

Something like: {username}-{proj}.tuns.sh. 300 IN CNAME myalb-123abc.amazonaws.com.