Sounds amazing, but I can see how you wouldn’t want to do that too often.
How I did it: I bought $14 worth of organic roma tomatoes from central market, fresh italian herbs, onions, mushrooms ect and looked a recipe up online. I boiled those suckers to remove the skins, then tried to deseed them and take out the water. Then I cooked them for what seemed like fricken forever.
Lessons & tips: don't do this unless you have a lot of time and aren't on a deadline.