That bothers me too when I think about it too long…
OK, I know, it’s my quirk, and I know, “Cooking is art; Baking is chemistry.” It’s just awfully nice when you can look at a recipe and see “1 can or 1.5 cups” or “1 can or 12 oz” and just plunge on ahead, rather than having to stop and think about whether drained weight vs wet weight is important to take into consideration or whatever.
A French-style omelet is cooked relatively fast and has more structure to it. It has to be stirred/shaken as it is made to keep it soft, make sure it is cooked through, and not have a tough brown exterior crust. Additions are generally not mixed in with the eggs but added after it has set and ready to be folded onto the plate. Even an American diner-style omelet shouldn’t have onions and such added to the egg mixture itself; that would be more of a “scramble” (as opposed to scrambled eggs).
But this is cooking, not law, so anything goes.
I don’t think it’s just your quirk, Ferret Herder. I hear it a lot. Even baking doesn’t have to be that exact, although its margin of error is much, much lower than, say, a stew. I think it just comes down to how you like to approach a task. I don’t think home cooking is well-suited for a very rigid, exacting, scientific approach, and I think flexibility and using your senses and judgment is absolutely necessary.
I’ve written down recipes before and said precise things like add “1/4 cup of sour cream” when what I really do is add a big glop and then add a bit more if necessary. People get really wrapped around the axle sometimes. I had someone ask “how many carrots per person should I add”? Big carrot or little carrot, sumo wrestler or ballerina coming for dinner?
How do you make things from scratch with tomatoes? I’ve tried making salsa, gazpacho, marinara, but it always is a watery mess, even just at the chopping stage. Am I supposed to only use a certain part of the tomato?
Also, what’s the scoop on non stick pans? Are there any that are really no stick and also don’t put cancer flakes in your food?
It’s the type of tomato. Commercial sauces use starchier tomatoes.
There’s a few things you can do to avoid the watery mess. You can do any/all of these to help:
Use Roma tomatoes. These are probably the least-watery of the commonly available tomatoes
Seed your tomatoes. It’s not as hard as it sounds. Just cut the tomato into quarters and use your thumbs to pull out the seedy bits.
Roast the tomatoes before using them. Just stick 'em under the broiler until the skins start to turn black. After roasting, scrape off the skin and scrape out the seeds. This does slightly change the flavor, so maybe is not appropriate for all recipes.
I totally get it, trust me. I love cooking without a recipe or even modifying a recipe on the fly without ever having made it before. It’s just that after a while, certain things stick in my brain - “does no one in that kitchen use dried beans?” “are they assuming dried herbs or fresh?” “why the fuck do none of these recipes use salt? This is from a high-end chef in Chicago, surely they would salt this,” “the directions are almost non-existent, so do they really mean 1 cup of pre-cooked brown rice when they say ‘1 cup cooked brown rice’ or did someone screw up and they mean ‘1 cup brown rice, cooked’ as in start with 1 cup dried brown rice and cook it?” I just try to muddle something out and plunge onwards. 
And by “seedy,” that means the “tomato goo” parts too, which may not have any seeds at all.
It really does make a difference. When I was canning tomatoes this summer, I mostly canned Romas, but had some that were other varieties, and a few jars where I got tired after something like 6 straight hours of canning and didn’t bother seeding them. I set the jars on the counter to cool, and you’re supposed to leave them alone for 12 hours to make sure the seal sets and they’re cooled and not going to break or anything. You could see where the non-Roma and non-seeded jars were just by the level of “water” that had settled out in the bottoms of those jars, versus much, much less “water” for the Romas.
Athena’s right, but, also, unless you get fresh tomatoes from your garden or a good farmer’s market, you’re better off using canned tomatoes. Most of the tomatoes I find at stores, even the Romas, are just flavorless watery goo.
When I use tomatoes from my garden, I don’t necessarily use Romas, and I don’t necessarily bother to peel or seed them, and the sauces turn out fine. Doesn’t work so much with supermarket tomatoes. I have pretty much given up on supermarket tomatoes for any sauce preparation.
Yeah, I always correct for salt at the end of a recipe. Doesn’t matter what the recipe itself says. I’m always tasting and adjusting towards the end of cooking (you can’t do it too much too early, as when something cooks down it becomes more concentrated and you might over season). As I say, use and trust your senses (which it sounds like you are doing.)
No harm if you use it fairly frequently.
One I’ve seen is: 1/4 cup fresh whole strawberries. How many is that, 3? 
A can of beans is anywhere between 1-1/2 to 1-3/4 cup drained beans. Depends on the brand. If you are talking about “El Cheapo” from the 99-cent store, there will be more liquid in the can.
You wanna make my eyeballs shoot out flames, give me a recipe that calls for 2 tablespoons of tomato paste.
IDIOTS! Cans of tomato paste are dinky. Adjust your stupid recipe to accommodate a whole fricken can! I don’t need little cans of half-empty tomato paste cluttering up my refrigerator, growing science projects while I sleep at night!
I’m not crazy about recipes that call for one cup of diced celery, or 3/4 cup chopped onion. Write your recipe in available “units”–one rib of celery, diced. 1/2 of a baseball-sized onion, chopped.
~VOW
I hate that too. I’ve started buying tubes of tomato paste. You can use just as much as you need. It’s more expensive unfortunately.
I do that as well.
Tomato paste also freezes very well. If I open a can and don’t use the whole thing, I drop it in tablespoon-size dollops on a plastic-wrap covered plate. Throw it in the freezer, when they’re frozen, throw 'em in a ziploc. Very handy to pull out just a tablespoon or so as needed.
I think I love you.
I get the tubes too, though I do freeze extra pesto in similar ice cube sizes. You can also chop fresh basil or cilantro and freeze them similarly, adding water (or appropriate oil) to the tray after you put the chipped herbs in. Not as nice as fresh but far better than dried.
Thanks!
You can do the same thing with canned Chipotles, another item that comes in cans big enough for several meals. Warning, though: frozen Chipotles look an awful lot like frozen dollops of tomato paste. Label them well.
Someone notify the Nobel prize committee - I think we have one of this year’s winners.
Why have I never thought of this? How many cans of tomato paste have I guiltily thrown out, half-empty, because my recipe only needed a little?
You have changed my life.