Ingredients:

  • 28 oz can Whole Peeled Tomatoes (San Marzano recommended)
  • 5 tablespoons Unsalted Butter
  • 1 medium Yellow Onion, peeled and cut in half lengthwise
  • Kosher Salt, to taste

Instructions:

  1. Prepare the Onion: Peel the medium yellow onion and trim the ends, then cut it cleanly in half from root to stem. Do not chop or slice further.
  2. Ready the Tomatoes: Open the can of whole peeled tomatoes. If using whole tomatoes, give them a quick hand-crush or use the back of a wooden spoon to break them up slightly in the pan.
  3. Combine Ingredients: Place the tomatoes (including their juices), the two halves of onion, the 5 tablespoons of butter, and an initial 1/2 teaspoon of salt into a heavy-bottomed saucepan.
  4. Heat: Set the saucepan over medium-low heat. Bring the mixture just to a gentle, bubbling simmer—not a rolling boil.
  5. Slow Cook (Crucial Step): Once simmering, reduce the heat to low. The sauce must bubble gently and steadily. Simmer uncovered for 45 to 60 minutes, stirring occasionally (every 10–15 minutes) to prevent sticking, until the sauce has thickened and the fat (butter) has separated slightly.
  6. Remove the Onion: Take the pot off the heat. Using tongs or a slotted spoon, carefully remove the two halves of the cooked onion and discard them.
  7. Season: Stir the sauce thoroughly to emulsify the butter back into the tomatoes. Taste and adjust the salt as needed.
  8. Serve: Toss immediately with cooked pasta, or allow to cool before storing.