I don't have the book in front of me, but I think there was a 'poisoned' option for claws, which might allow for a lingering 'burning' effect.
Just looked it up. Venomous. It's pretty Brutal. I'd do it like this:
Burning Hands permanent ritual
-1 Claws
-2 Venomous
+1 Human Form
Total: -2 refresh
A character with this power could light his hands on fire as a free action. When fighting, he can make a fists maneuver to set an enemy aflame, allowing a free fists vs. endurance attack every exchange. Also, he gets +2 damage on his normal fists attacks, ala Claws.
It's pretty cool. I'd take it for the right character.