Dice the onion and mince the garlic. Add the onion, garlic, and olive oil to a sauce pot and sauté over medium heat until the onions are soft and translucent (about 5 minutes).
Add the tomato paste and continue to stir and cook for 3-5 minutes more, or until the tomato paste takes on a slightly darker color. This caramelizes the sugars in the tomato paste to give it a slightly sweeter and less acidic flavor.
Add the crushed tomatoes, basil, oregano, brown sugar, and salt to the pot. Stir to combine and dissolve any tomato paste from the bottom of the pot.
Allow the sauce to come to a gentle simmer, then reduce the heat to medium-low, partially cover the pot, and allow the sauce to simmer for about 30 minutes, stirring occasionally.
After simmering for 30 minutes, taste the sauce and adjust the salt, sugar, or other seasonings to your liking. If the sauce is too acidic for your liking, you can let it simmer longer (about one hour) or add more sugar. Serve hot or refrigerate until ready to eat.
*Garlic pairs so well with tomato sauce that I just had to add some to round out the savory flavors. That being said, you can skip it for a more traditional marinara sauce flavor.**You can use any brand of canned crushed tomatoes. But, if you want to get a bit fancier, you can opt for a premium or imported brand, or even buy whole canned San Marzano tomatoes and purée them yourself. If you can not get crushed tomatoes where you live, passata will also work.