A good amount of the time, when I'm making something that has origins in another country or on another continent, I try and stay relatively authentic to how people would make the dish back home. This isn't one of those times.
The problem with making "authentic" Italian food is that tomatoes didn't enter the equation until they were imported to Italy from America. What we know of as modern Italian food is almost as much of a hodgepodge of things from different places as American food is, so you might as well just do it however it's gonna come out best without worrying about how hard your friend's nonna will hit you with her purse when she finds out. Speaking of tomatoes, the popular opinion is that San Marzanos are the best choice; which is generally true, but not by as big a margin as you'd think from how people rave about them. They're better because the ratio of "meat" to jelly/seeds is higher than other tomatoes, but having tried making sauce with both I don't think it's worth the higher cost of the SMs to bother going that way. The other way tomatoes usually factor into sauce is through tomato paste. It gives the sauce a bit of an umami kick due to the monosodium glutamate (the stuff stupid people used to bitch about before gluten became A Thing) naturally present in tomatoes being concentrated by reducing them into the paste. I don't usually keep tomato paste around the house because it usually goes bad before I get a chance to finish it; but I do keep miso paste around, which has a similar effect but does make the sauce taste slightly different in a good way.
As for the meatballs, I tried making them the usual way and they came out dry; so I shifted focus to using things that would keep the meatballs together but then melt once they went into the oven. That's where the slightly unorthodox beef gelatin came into play. I use store-bought broth mainly because we use so much of it that if I went homemade all the way I'd spend all my time not cooking other things making different stocks. The difference between stock and broth is that stock is made by simmering roasted bones (which have gelatin in them naturally), and broth is made by simmering meat. If you make your own stock, there will be gelatin in it that's come out of the bones so you would just have to add it to the meatball mix cold, and it'll do naturally what I had to do artificially. If, for some reason, you make your own broth, you'll need to add the gelatin before using it for this recipe.
One last note: it's important that you follow the last step of letting everything cook a bit more in the sauce pan at the end, because if you follow this recipe and then just combine everything on the plate then the pasta and meatballs won't be fully cooked.
1/2 a box of spaghetti (if you're trying to get whomever you're making this for to fuck you, make it fresh )
2 cans of whole tomatoes, pulsed once or twice in a blender before putting them in the pan so they smooth out but you still have a few small chunks of tomato in there
1 teaspoon of white miso paste (it's called white, but it's actually yellow/brown)
1/2 teaspoon of celery seed
3/4 teaspoon of oregano
salt and pepper to taste
3 bay leaves
about a cup of water (give or take a couple tablespoons, ya gotta go by eye)
1/2 pound of ground beef
1/4 cup of milk
1/4 cup of beef stock/broth
1 packet of gelatin (optional depending on whether you're working with broth or stock)
about 1/2 teaspoon each of salt, pepper, oregano and celery seed (I usually eyeball it by sprinkling once over the entire surface area, but if you have a tendency to accidentally over-pour spices then measure it out)
1/4 teaspoon each of garlic powder (or 1 clove of garlic diced as finely as possible) and onion powder
1/4-1/2 cup of Parmesan cheese
1/4-1/2 cup of breadcrumbs (I used Panko because that's what we had around, use whatever you like. Fresh breadcrumbs are best, where you toast a piece of bread and then run it through a food processor but I was doing a lot of shit today and didn't have time)
If you're doing the gelatin step, prep it with the beef broth however it says to do so on the box. Generally it'll be some version of combine, nuke for about 30-40 seconds, let it sit in the fridge for a bit but make sure first.
Combine all the sauce ingredients in a fairly large pot or pan. Don't use one that's almost full at the start because the pasta and meatballs are gonna go in there at the end so you'll want some room. When adding the miso paste; you can either put it right in the pan in quarter-teaspoon sections spread over different areas of the pan for even coverage, or whisk it into the cup of water until it's fully incorporated. The problem with that second method is that if you only end up needing a half cup of water to get it where you want it, you'll have to add more miso paste and waste whatever went into the water you didn't use. When adding the water, judge visually how much you want to use. I add it until the sauce is just a little bit too watery for my tastes because it's going to simmer and reduce from there so you don't want it to get too dry. Add a little more water than you think you should and it'll be perfect by the time you're done. If it starts looking too dry later on then you can always add some more water. Mix everything together well, get it to a light simmer, and leave it alone for a while. Go back and stir it around whenever you remember to.
Pre-heat the oven to 350 degrees. Oil a fairly large baking pan either with spray or oil wiped on with a paper towel. Pull the stock jelly out of the fridge (if it's not fully set, don't worry about it, the solid parts of the meatball just need to be solid enough that you don't need more breadcrumbs to offset them as a wet ingredient); and crack the egg into the bowl and whisk it around with a fork a little bit, but just enough to break the yolk so you don't overmix it when the other ingredients go in. Pour in the milk and spices and whisk it some more, then add the cheese and breadcrumbs and stir until it's smooth. If it's too liquidy, add more cheese and breadcrumbs a tablespoon or 2 at a time until it resembles a very thin paste without any free-floating liquid, but doesn't offer resistance when you stir. Break up the ground beef as small as you can without putting too much work into it, and get in there with your hands to combine everything until it's all incorporated evenly. Roll the mixture to about 12 or so golf ball-sized meatballs, and arrange them on the pan so they're evenly spaced with about an inch or so between them. Bake them for about 20-25 minutes (if they came out a bit bigger than golf balls, err towards the 25 minute mark); or do what I did and set the timer for 20 minutes and be in the middle of something when it goes off so it's more like 22 minutes. Once they're done, remove the bay leaves from the sauce pan and toss the meatballs in.
When the meatballs go into the oven, start a large pot of salted water on a burner on high heat and bring it to a boil. I break my spaghetti in half to make it a bit more manageable but whether or not you do that is up to you. Cook it until it's almost done but not quite, and then reserve about a cup or so of the salty, starchy water. If the sauce has tightened up too much, use that water to thin it out a bit rather than regular water. Drain the rest and transfer the pasta to the sauce pan. Make sure the pasta and the meatballs are well incorporated into the sauce.
Once everything is in the sauce pan, put a lid on it and cook it for another five minutes or so while you get the plates and everything ready. When it's all done, take out a serving of the pasta with tongs and put it on an appropriately-sized bowl or plate, giving it a bit of a twist when you place it on. Arrange the meatballs on the side in a way you think looks nice, serve with some extra sauce if needed and a bit of Parmesan over top of everything, and enjoy.