Gather all ingredients.

Mix together whole tomatoes, mushrooms, tomato sauce, tomato paste, water, onions, basil, garlic, sugar, 1 pinch of baking soda, salt, and pepper in a large saucepan. Bring to a boil over high heat while stirring, then reduce heat to a simmer, and cook for at least 4 hours.

Stir in remaining pinch of baking soda; sauce will foam. Simmer, stirring occasionally, until thick and almost brown. Make sure to scrape the sides of the pan into the sauce.

Stir in Parmesan cheese. Taste sauce: if too tangy or acidic, add another pinch of baking soda and simmer for 30 more minutes.

Let sauce cool to room temperature, then cover and refrigerate for 8 hours to overnight. Reheat the next day and serve.