Heavy load DNS server

Hello All
I have heavy load DNS server with

OS: FreeBSD amd64

Version: 12.3-STABLE

CPU: Intel(R) Xeon(R) CPU E5-2620 v2 @ 2.10GHz

RAM: 16014M / 16354M

Processes: 45

How do i optimize this server
Now if I run htop the cpu usage is 190%