Preheat oven to 350F (175C)
Bring salted water to a boil in a medium pot. Cook the spaghetti according to the package until it is al dente, about 12 minutes. Drain the pasta.
While the spaghetti is cooking, heat up a large saute pan over medium heat. Once pan is hot, add the beef and onions. Break up the beef into chunks and cook until the beef is brown and the onions are transluscent, about 6 minutes. Remove from heat.
(Optional) drain the excess oil from the pan. I kept in the oil for flavor but feel free to remove if desired at this point.
Add the spaghetti sauce and salt to the pan, stirring until the mixture is fully combined.
Melt the butter in the microwave, in a microwave-safe bowl, using small increments (around 5-10 seconds).
In a large bowl, whisk the eggs. Add the butter and parmesean, and stir to combine. Add the pasta and stir, ensuring the pasta is evenly coated with the mixture.
Lightly grease a medium cast iron or 9x13 baking dish. Add half of the pasta to the dish. Layer half of the cottage cheese on top of the pasta, then half of the sauce, then half of the mozzerella. Repeat with the remaining pasta, cottage cheese, sauce, and finally top with the remaining mozzerella. Cover the dish with aluminum foil.
Bake in the oven for 40 minutes.
Remove the foil and place in the oven again. Once cheese is golden brown and melted, about 25 minutes, remove from the oven.
Serve this at your next Heroes' Feast, enjoy adventurer!