Eggs, of course, it takes about 1 minute? Never checked but it should be enough for a soft scrambled eggs or sunny side up on my induction cooker. I could eat an egg or 2 or 3 raw anyway, without doing anything bad to my biotin, at that.
Well if I am hungry, 3 eggs just make me hungrier (though nowadays my satiation is easier. still, I probably still need 10? still a tiny meal but may be enough for 1-2-3 hours. BUT I never ever ever ever could eat 10 eggs made in the same in one sitting, I get bored) even with a generous amount sour cream and cheese on top but if I have some sausages, that can be fine.
I have cottage cheese too now, I will try it mixed with eggs, it must be a big thing according to the Internet…
If it can be keto, I only have a single idea: cake. But I never want cake when hungry. So it’s for the times when I am satiated but want to eat something? But then I get hungry and need to cook something else… Whatever. 5 minutes keto food, cake. I probably can do it in 1.5 minutes in a pinch, only my tiniest, special one though (one yolk and 10g gound walnut as the base, super tasty).
I can’t think of anything else, I like cooking and did a proper lengthier one even when I went home after overwork at 10pm (it was simple but took time).
If I had very special meat that doesn’t need 30-200 minutes to cook, that could be an option (I remember beef liver taking ridiculously little time) but I almost never have.
If it’s not cooking, that’s simple. ANY carnivore ingredient beyond raw meats (sadly, I have no edible raw meats, they are great though). I could make a girl dinner from my fridge on most days. Multiple kinds of cheese cubes, some drier sausage, some butter, whipped cream, sour cream, Greek yogurt, cottage cheese, quark flavored with things (some cream does good too)… If I throw in some 98% fat smoked cooked pork, it can be an OMAD meal… And I very often have boiled and potentially pickled eggs. But as I wrote, eggs are almost no time to cook and I prefer almost any pure egg dish over boiled egg (and I gladly eat boiled egg when hungry. usually).
I have tinned fish too but I end up not using them for ages for reasons (like super fatty sugary sauce. I only have tuna but it needs a ton of added fat and it’s a chore to figure out how, anyway, it’s expensive and tuna is overfished, my SO says and well, I can eat so much better food. I do like a proper tuna spread, I just never did it fully right. hard to learn if I open a tin once a year).
I used to keep some fried meat in the freezer but I don’t anymore for reasons. So if I run out of meat and want meat, it’s basically always sausages. I do have tiny bacon cubes for my scrambled eggs but that’s over 5 minutes.
I only need a little extra or premeal though. I am aware I probably eat every day (it’s the case since YEARS
) so I plan and prepare food every day. A lot. 5-6 courses dinner and stuff, I need variety, NO WAY I only eat one dish or two, it just never happens (except my super rare breakfast when I eat one egg, virtually always), I don’t know how others do it… Must be nice. I may fry a pound of my favourite meat, I still need a lot of other varied food.
But in the past, I used to need some extra when I ate up my planned food and occasionally I really try to go for a fast day so I can’t have ready to eat food beyond my usual ingredients (or else I probably will eat it) and when I apparently inevitably get hungry, I need something. It’s fine if it takes 30 minutes though, that’s not a big deal to wait.
Oh, cheese whisps! About 2 mins but it’s a snack, not for my hunger.
Nuts are nice but my SO is the one who can eat 120-250g peanuts and calling it a a meal… It’s snack to me. Sometimes I eat 2-20 grams on a hike but I am very satiated then, just can’t stand him eating ALL the tempting nuts… Half a peanut is loads better than nothing if you ask me. Well if I am really modest, I just smell it… Love the smell of roasted peanut. But the smell isn’t crunchy 
I like tuna and probably would be upset if my eggs turned out to be fishy so I am not sure there is a connection… Never had fishy eggs so IDK but sounds very odd even for savory dishes (it may clash horribly) but I have them in my coffee and sweet baked goods…
I have eaten about 2500 eggs per year for decades (and it wasn’t a small amount for the rest of my life), I am used to the normal lovely egg taste
By the way, I have black salt (2 kinds, normal and Himalayan). What on earth one does with it when they aren’t vegans who never had egg so it’s not for the egg taste (they fail horribly, by the way). Should I just use it as salt in dishes that can handle the very strong taste…? Well it lasts forever, I have time to figure it out.