Can someone please help me with what happened tonight?

My wife and I have a great relationship, but she has the tendency to blow up on a seconds notice when I don't do what she expects. Tonight, I was making a fire in the fireplace so we could grill some steaks and went outside to get the wood. When I came back in, she told me that "a plate of lasagna hit me in the head, can you come see if I am hurt?" I responded, "if you have to ask, then you aren't hurt". I proceeded to the fire. Then I thought twice because I know she can blow up, so I asked "are you ok?" She said she didn't know, but obviously she was fine so then I asked if the lasagna was ok and laughed. "You are an , you don't even care about me" and she storms off to the computer. So then I made a huge deal about looking at her head and told her to show me, which she wouldn't....so I told her to "show me or we are going to the emergency room". She wouldn't, so I started poking at her head saying "is it here, is it here" (calmly) and she punched me, so I left for 3 hours and here I am. Any thoughts are appreciated.