What do I feed a domestic rabbit?

While mowing the lawn we found a rabbit eating dandelions. It is clearly domestic, as it doesn't look like any of our wild rabbits, and easily let us catch it.

We gave it a lot of water, a bit of romaine lettuce, and about a 1" piece of banana.

The animals shelter is closed for the night. It hasn't touched the food. Can I pick dandelions for it? I don't want him to die overnight, but we have hawks in the neighborhood and he would not have lasted long if we didn't catch him.