Homemade Tomato Sauce - Once Upon a Chef

Ingredients

• 4 pounds plum tomatoes (or two 28-ounce cans whole peeled plum tomatoes)
• 6 tablespoons unsalted butter
• 4 tablespoons olive oil
• 2 medium yellow onions, peeled and cut in half
• 4 cloves garlic, peeled and smashed
• 1¼ teaspoons salt
• 1 teaspoon sugar
• 2 tablespoons chopped fresh basil