Heat the olive oil in a large dutch oven or stock pot over med-high heat. Add the onions to the oil and cook until softened. Add the garlic and cook for one minute.
Stir in the oregano and then add the wine. Cook until reduced by half and then add the sugar, fish sauce, tomato puree and crushed tomatoes.
Stir the mixture until well combined and then add the salt and pepper. Turn the heat to low and cover. Simmer for 10-15 minutes.
Notes
Marinara sauce can be made up to 5 days in advance and stored in an airtight container in the refrigerator. Reheat in a saucepan over low heat until warmed through.To freeze marinara sauce, transfer to a freezer safe container and freeze for up to 3 months.