Before all else, fill up a pot of water and put it on the stovetop on high (add salt to the water if you like). In a large separate pan, heat the olive oil over medium heat.
NOTE: Skip this step if using jarred marinara
While the oil is heating up, chop the onion and mince the garlic. Add the onion and cook for 3–5 minutes, or until soft and translucent. Stir in the minced garlic and cook about 10-20 seconds, being careful not to burn it. Add the ground meat to the pan, breaking it into small pieces with a spoon or spatula. Season with oregano, salt and pepper. Cook until browned and no pink remains, about 5–10 minutes.
Pour in the crushed tomatoes (or 4 cups jarred marinara), stirring to combine everything. By now the pasta water should be boiling, so add in the pasta and set your timer according to package instructions. Reduce the heat to low on the meat sauce and let it simmer uncovered for 20–30 minutes, stirring occasionally. This allows the flavors to meld and the sauce to thicken.
Drain your pasta when it's ready then return it to the pot. Taste the meat sauce and adjust the salt and pepper as needed.
Serve the meat sauce neatly over the pasta, or mix it all together in the large pasta pot. Garnish with grated Parmesan or sharp cheddar.
Refrigerate any leftovers in an airtight container for up to 5 days, or freeze for up to 3 months.