Grease a large 12x12 baking dish (or something similar). Preheat your oven to 350°F (175°C).
First you will cook your pasta. Fill a large pot with water; lightly salt. Once boiling, stir in your dry pasta, return to a boil, and cook around 7 minutes (until pasta is cooked through but still firm). Drain in a colander and set aside.
Heat a large pan over medium heat, add your ground beef or sausage, and cook until browned. Drainy any excess fat, and set aside. (If your sausage is in a casing, squeeze it out of the casing and only cook the innards)
In a large bowl, mix together the onion, egg, ricotta cheese, garlic, and oregano. Add the cooked pasta, the cooked meat, ½ cup of spaghetti sauce, salt and pepper, and mix until everything is well-incorporated
In your prepared baking dish, start with a layer of spaghetti sauce, using about a ½ cup. Next layer will be half of your pasta & meat mixture. Spread everything out evenly until adding your next layer.
Continue layering with ½ of your shredded cheese, then the remaining pasta comes next. Add another ½ cup of spaghetti sauce, and then the remaining cheese
Cover your dish tightly with aluminum foil, and bake in the preheated oven for 20 minutes. After this time, remove the aluminum foil, and cook for 10-15 minutes, until all cheese is completely melted.
(Let your dish cool for 10 minutes before serving. Enjoy with a green salad and a nice glass of red wine.)