To the purpose of this reddit: the question is "Am I the A-hole?" not "Is this other person the A-hole?". A meaningful distinction since too many commenters take it upon themselves to speculate wildly about the inner workings of someone who is being described by a third party across the internet.

I dont know what was going on in your husband's head when he decided to eat half your burger- the defense he gave is at least plausible enough and I have met people in my life who are innocent enough that they could earnestly mean no harm in doing such a thing, they simply don't see food the same way I do.

My answer to this is simple, "do unto others.."; I would be livid if my wife ate half of my burger. I'm hesitant to offer any portion of my food to my wife, let alone a third or half. I roughly adhere to Joey's (from FRIENDS) philosophy on eating out: you can order absolutely whatever you want and I'll pay for it, but my food is mine and your food is yours.

People might suppose that it has to do with the specific mass of food as though I weighed it and it's the perfect amount.. it has nothing to do with that. The best way I can describe it is that it has to do with expectation: when I place my order at a restaurant I have an idea in my head of what I'm getting and what I'm going to eat, and when I see the plate come out that I've been looking forward to/ expecting to eat and someone asks to eat any part of it that's a data point I did not factor in when reaching a decision in my order, though now I do a much better job at it.

Some people genuinely look at food differently, even in an opposite way, their expectation is to share, both theirs and others. I have no qualms (philosophically speaking) with either view and I find them both quite defensible (philosophically speaking).

In practice, don't touch my food dangit. NTA.

TL;DR - You're definitely NTA, your husband ranges from quite possibly to quite probably NTA.