Let me try to explain. I have certain food items that I really dislike. I am not allergic to them, but their taste I just can not bear at all. They include some foods that people tend to have in too many meals, and the best example is onions (in any way, green onions, leek, cooked onions, etc.). Overall I am not a very picky eater, but even a tiny bit of onion will spoil any dish for me. I know I am not alone in this, I have several friends also totally disliking onions, but in general people like them, obviously.
So whenever I am at a restaurant and I have to mention food should be cooked without onions, they sometimes forget it, then I remind them I asked, and the waiter either says something like: "But it compliments the dish!" or "But there's not much of it!", or they pick the most obvious pieces out, but it remains there.
Whenever I am with friends or I meet new people in a friendly gathering and someone cooks for everyone, every time I am being mocked - in a friendly way, but - about it. I have, unfortunately, zero sense of humor, even though I try to cultivate it and am a good-natured person, so I can never think of a witty or a proper answer.
Whenever I am visiting my granny, she loves to cook for me (as grannies are) and at every single meal there will be a talk how I should try onions and how food is not eatable without them and so on and so forth.
I know this is my own problem, but I get really frustrated from all these comments and situations. I know I can not change everyone around me. I can definitely not change granny or any new people I meet, and I can not force my friends not to joke about it since it's their way of expressing friendliness towards me, light jokes. But it seriously angers me and makes me feel like an idiot. I can not control my food dislike, that's a given.
Any advice of how I can behave in such situations? Maybe how to answer properly to stop the conversations at the very start, not being too rude, but effective? I hope I have made it clear enough.