Place a large skillet over medium heat. Add the butter and oil to the pan. Once the butter is melted, add the white parts of the onions, garlic, and parsley to the pan. Cook until fragrant, about 1 minute, stirring occasionally.
Add the tomatoes, lemon juice, salt, and pepper, and stir everything until combined.
Bring to a simmer and then simmer for 15 minutes stirring occasionally.
Add the fresh basil and green parts of the onions to the sauce. Stir to combine.
Take off the heat and serve with pasta of your choice. We like to add a big sprinkle of parmesan cheese on top too.
Notes
If you don't have salted butter on hand, you can use unsalted butter and add an extra 1/8 teaspoon salt to the sauce when you add the salt and pepper.
Store any leftovers in an airtight container in the fridge for up to 3 days or freezer for up to 3 months.