Tough situation. Is this the first time she has ever gotten physically violent with you or is this repeated behavior?
If it's the first time then I think it's important to speak some hard truths to her, letting her know that this behavior is unacceptable. I would suggest using the communication tool
SET with her.
Maybe start by saying something like, "I understand that at times you get angry with me and it's important that you are able to express your anger. I want us to be able to talk through our issues. Physical violence is unacceptable. It is abusive and I don't like it. I don't want our son to be exposed to it. I know that I can push your buttons at times and that angers you. Understand though that even when I frustrate you, I love you and you are important to me. Can we agree that violence will not be a part of our relationship?"
If she is unwilling to agree to not being violent or if she becomes violent again, what will your next step be?