Question regarding punctuation within dialogue

Me again! This one is kind of lame, but it bothers me.

Is there a proper way to punctuate a sentence of dialogue in which a particular phrase/word is repeated and also interrupted by writing that isn't dialogue (i.e. -- "he said"). That probably doesn't make sense, so please see the following examples:

"Right now," he said. "Right now I could go for a cheeseburger."

Does that seem correct? Or would it be something more like:

"Right now--" he said, "right now I could go for a cheeseburger."

or . . .

"Right now," he said, "--right now I could go for a cheeseburger."

I hope my question is clear.

Thanks for your help!