I recommend letting the bunny get used to the dogs scent before there is the possibility of any contact.
Show your dog the bunny in the cage from a distance- be sure to not let any nervousness or tenseness transmit to your dog since you dog might think the bunny is making YOU nervous and it is a reason to be defensive. Give your dog a couple of treats if the dog will break from looking at the bunny to look at you.
What kind of dog do you have?
I have 2 Australian Shepherds that are awesome with my bunnies- they are only together if I am home since the bunnies can not free run the whole house. But since I have other pets- the dogs seemed to look at the bunnies and think “OK, they belong here”. And then once they figured out that bunnies produce wonderful little treats (bunny poo) they soon became more interested in looking for poos on the floor to eat when the bunnies are out- more interested in the poo than the bunnies themselves.
But it is also important to see how your bunny is with the dog- the bunny needs to learn the scent of the dog. So I would let the bunny get used to the surroundings and smell of the dog before you let the dog approach the cage. Then eventually let the dog approach the cage and guage the bunnies reaction to see how long before you can move onto a controlled intro.