Heat oil and ghee in a large skillet over medium. As soon as ghee is melted, add onion and a pinch of salt and cook, stirring occasionally, until softened, about 5 minutes. Add garlic and cook, stirring occasionally, until garlic is very soft, about 5 minutes. Add basil and as soon as it is wilted, add the tomatoes, crushing well with your hands as you go. Bring to a gentle simmer and cook sauce until thick and flavors have melded, 20–25 minutes. Season sauce with salt and pluck out basil.