How do I get to root on pfSense?

I am running pfSense 21.05.2 in AWS. I can ssh in as ec2-user, and I can see that the sudo package (0.3_6 with a dependency on sudo-1.9.7) came pre-installed. In the web interface, under System > Sudo, I can see the ec2-user has Run As privileges for root and No Password is checked and the Command List is ALL.

This is the behavior I observe in the shell:

> whoami
ec2-user

> sudo su -
su: Sorry