Chop 1 onion and put it in a pot.
Add 1 or 2 cans of diced tomatoes. Whatever makes the ratio of onion look right.
Add a ridiculous amount of frozen peas. Peas should make up a notable portion of this sauce.
Add frozen corn also if you wanna be real fancy. If I have bacon, I'll add that too, but I very rarely have bacon.
While sauce is cooking, grab the nearest bottle of mixed spices that isn't obviously for desserts. Add some. How much? I dunno, enough that you feel like you've added seasoning so it's technically cooking. (For me this is most often a mix called Moroccan, but it could be anything. I've reorganised my kitchen recently so tonight it was something called Pizza Topping.)
If you happen to have green herbs lying around, add those too. Whatever you have on hand that's green.
Let the sauce boil on HIGH until all the water is gone. Stir occasionally so the saucepan will be easier to clean later. Serve on cooked spaghetti noodles with no cheese.
Today I added a new step called "while the sauce is cooking, duck out for 15 seconds to post about spaghetti sauce on Tumblr, then get distracted and forget you are cooking." This adds a novel Extremely Burnt edge to the flavour profile.