Heat the oil in a large saucepan over med heat. Add the onion and cook, stirring occasionally, until softened., 4 minutes. Add the garlic and basil; cook, stirring constantly, until fragrant., 1 minute. then add the tomato, pepper flakes and salt, bring it to a boil. reduce the heat and simmer until thicken stirring to avoid sticking. Stir in the parsley..
Transfer 1 cup to container and cool for 4 days for later use..