Add peeled tomatoes and tomato paste. Before the sauce gets too hot, use your hands to crush up the whole tomatoes - this is the way my grandparents did it - until they are broken down into smaller chunks. Add salt, pepper, and dried herbs to taste.
Allow sauce to simmer on low until you are satisfied with the taste or until you are too hungry to wait anymore; a minimum of 1 hour, but I simmered my sauce for about 4 hours and it came out incredible.
Just before serving, add fresh basil and parsley to taste.
Recipe by The Two Bananas at https://thetwobananas.com/4-cheese-spinach-mushroom-lasagna/