Peel the onion and garlic, then crush the garlic and dice the onion.
Heat oil in a heavy-bottomed saucepan over medium-high heat. Sauté onion and garlic for 4-5 minutes.
Crank open a can of tomatoes and pour into the pan. Stir in oregano, olive oil, red pepper flakes (optional if you want to make it spicy add 1 tsp), and salt.
Reduce the heat to low and let simmer for about 25-30 minutes, or until liquid is reduced by 1/3 and oil gets separated from the sauce.
Remove from the heat and carefully transfer it into a stand blender, together with the fresh basil. Blend until smooth, or until it has reached the desired consistency.
Taste and adjust the salt according to your taste. Transfer the sauce into an air-tight jar secure with lid.
Serve with your favorite side. This sauce can be refrigerated for up to 5 days and freeze up to 6 months.
Notes
Tomatoes: Any style of canned tomato is fine, but San Marzano tomatoes have the best flavor because they are grown in Italy and picked at their peak of ripeness.
Garlic: Freshly chopped garlic is preferred, but you can use jarred garlic in a pinch. We recommend not using garlic powder as it can add bitterness to the sauce.
Onion: You can use a yellow onion, or a Vidalia or Walla Walla onion to give your sauce a little bit of sweetness.
Oil: You can use Avocado oil, Olive oil, or butter for keto.
Cheese: For a kick of flavor, add a bit of freshly grated parmesan cheese to your sauce before pureeing. You could also add nutritional yeast if you want the cheesy flavor but want to keep the sauce vegan.
Don't overcook the garlic: you don't want to burn the garlic so it doesn't give a bitter taste.
Storing: It can be stored in a container and placed in the fridge for up to 7 days. Reheat in the microwave when ready to eat or added to pasta. You can freeze for up to 4-6 months.