Whether you eat 5g or 50+g of carbs in ketosis, some one food (over time) contributes more to you carb consumption than any other. After a long time on chronometer I checked and it is clear for me.
ONIONS!
I love them sauteed with meat, spinach, and most every savory dish I cook. Almost twice as high as #2, tomatoes. After those two, which nearly account for 50% of my carbohydrate consumption. It is a whole bunch of different things.
Iāve always considered onions to be a āfreeā food. While they have carbs in them, they donāt cause me any cravings, or any negatives for that matter. And I didnāt get fat eating onions.
I donāt keep track enough to know, and I eat too many different things per week. This week, for instance, my lunches are ham steaks from a mangalitsa pig. Added fresh salsa once and olives, and just olives once.
Next week, Iāll have something completely different.
It depends. On the days with 7dl milk, itās milkā¦ (I thought those days are over but nope.)
On my best days, itās eggs.
And off days can do anything but itās about keto days, right? 
(7dl milk is totally keto for me, even carnivore-ish most of the time. And such days happen very, very rarely.)
But for the average keto day of mineā¦ I looked at my notes hereā¦ Does dairy count as one? It may or may not be a bigger contributor than eggs, it depends how I like to eat that time and what I haveā¦ On a normal day eggs bring more carbs but I have very carby days with much dairy so if we look at the average, dairy may be the first unless I have a really low dairy phase.
It itās separate items, eggs are the winner.
I loved onions but I probably didnāt use them sooo much even on normal keto let alone during the years where I usually tried to stay close to carnivore as much as it was comfortably possible. My stews have it but thatās a few grams of carbs 1-2 times a month. I get the same amount from eggs every dayā¦ Itās another matter that I consider my animal carbs pretty much irrelevant as I feel the same getting 3g or 20g or more.
On my original keto it was vegs, 25g net carbs a day (I remember making sure I use up my allowance in order to limit my dissatisfaction with my super tiny veg intake. I missed my vegs, I only could ate 1kg a day or something, less than minimal for me. and thatās the reason I ate 40g net carbs on keto. and because I could). Next was oily seeds. Then eggs, then fruits.
I often eat liver but the average is still only 1g carbs per day, eggs win easily. Egg only lose 1-3 days per month against liver.
Itās difficult to pinpoint one. I usually have a salad with dinner. There isnāt a lot of one vegetable, but I usually include a bit of cucumber, mushroom, olive, onion, maybe a bit of avocado, and of course the lettuce itself. I donāt think of it as having carbs because these are low carb veggies, but they do add up.
And I will have the occasional 1/2 cup of blueberries as a treat.
I was also appalled to discover that my cocktail sauce contains 18 g in a quarter cup. This is a super hot sauce and I doubt I eat more than a tablespoon, but thatās still 4.5 g. Somehow the fact that itās so almost unbearably spicy caused me to overlook the label. 
dairy or seafood when I do choose to eat it. but for me it is āall animalā so where those few carbs come mean 0 to me literally. All meat protein wrapped goodness around the few ācarbsā I might eat are all carnivore so, again, mean squat but yea, I do āhave a trace of carbs in eggsā but again, 0 plant so they never register ever to me. JUST me on this one being zc.
I used to add onions, but these days, when I eat veggies, it may be broccoli, asparagus, arugula, or Cleveland Sour Kraut (garlic). I donāt eat veggies nearly as often as I used to because they just donāt seem to add much to my meals anymore. But I will eat them when I sit down to eat with my family. But my sons are young adults now, and they really donāt bother much with veggies either unless they are cooked with bacon or bacon grease or cheese.
Even though I sometimes crave a batch of caramelized onions, my carbs are a battle when I have brussel sprouts. They are about 1 carb per little head. When hot counting, I can eat many. But for my lunch today I only allotted my self 7 (sad) and added butter, diced prosciutto topped with shaved parmesan cheese.