Dietpi Persistent Route

I am finding that when I try to set a persistent route in dietpi it is only good until power is lost.

I used the following command:

sudo ip route add via

This works with reboots just fine but when I lost power the config was lost and it took me some time to figure out that the route being lost was the problem.

I tried adding the following to /etc/network/interfaces but it broke my traffic all together:

# Ethernet
allow-hotplug eth0
iface eth0 inet static
up route add -net gw dev eth0

What is the correct way to add a permanent route on DietPi?