It's marvelous for pasta, and you can make primo meatball subs with it as well. You can alter it in a number of ways, but I urge you to try it just as described here before you go experimenting.

Equipment

Large (48 oz top, minimum) double boiler with lid — preferably stainless steel
Stirring spoon
Measuring tablespoon
Measuring teaspoon
Optional, but awesome to have, infrared temperature measuring instrument (Like this ) This is one of my absolute favorite tools to have in the kitchen.

Ingredients

2 tablespoons olive oil
1 tablespoon minced garlic
2 tablespoons of Hunt's tomato paste with Basil, Garlic & Oregano (...this stuff )
1 pinch of kosher salt
1 tablespoon red wine (merlot), plus...
½ cup of red wine (merlot)
1 eight ounce can of tomato sauce
1 thirty-two ounce can of crushed tomatoes (ideally, San Marzano tomatoes, but anything will do in a pinch.)

Directions

1: Place the top section of the double boiler over low to medium heat. It will be placed on the bottom portion after the initial higher temperature cooking of the ingredients. At the same time, heat the bottom section of the double boiler and its water on a different burner, aiming to get it to boil. Keep an eye on it; once it boils, immediately reduce the heat so it settles down to only steaming a bit.

2: Once the top section is hot (aiming for 160°F), add 2 tablespoons olive oil, then swirl until the bottom is covered with the olive oil.

3: Add 4 teaspoons minced garlic;

Cook and stir for 2 minutes. The objective is not to brown the garlic. It'll smell great.

4: Add 2 tablespoons canned tomato paste; Add 1 pinch of kosher salt;
Stir and cook for 2 more minutes.

5: Add 1 tablespoon red wine (merlot); The purpose of this tablespoon is to deglaze the pan with just the initial ingredients in it.
Stir and cook for 2 more minutes.

6: Add eight ounces tomato sauce;
Add thirty two ounces crushed tomatoes;
Add ½ cup red wine (merlot)
Stir until wine is well mixed with the sauce.
Cover the top of the double boiler now.

7: Place the top of the double boiler over the bottom section. Adjust the heat to low — aim for 150°F to 160°F maximum for the sauce. Tip: The reason a large double boiler is used is so that burners can apply less overall heat; typically, an electric stove does not have a low enough setting for a small double boiler to hit the temperatures we're after here, and an induction burner such as I am using creates very high peak temperatures which must be buffered by the water in the double boiler. A larger double boiler ensures that a lower temperature can be achieved with good control.
Do NOT allow the sauce to simmer. If it's bubbling, it's too hot! ^{See notes A,B below}

8: Cook at 150°F to 160°F maximum for (ideally) 8 hours; minimum 4 hours. Make sure the bottom of the double boiler does not go dry (tip: it won't if you're using a large enough double boiler.) The heat should be set so the bottom section is no longer boiling, just gently steaming. The aromas... well, you'll see.

9: (Optional ) About 4 hours before the cook is done, you can add either pre-cooked meatballs and/or pre-cooked sausage and/or mushrooms. This gives them time to add flavor to the marinara, but not enough time to lose their identities.

A) Here's the problem with simmering. If your marinara is simmering, you'll see bubbles rising slowly. What this means is that the sauce on the bottom is boiling hot. That will overcook the tomato content, and the sauce will darken and the chemistry will change, and not in your favor.

B) Food safety: You don't need to let this simmer to make it safe; all of the canned tomato ingredients are safe to start with. The garlic, if fresh, is the only ingredient that needs to be cooked more fully and that's the first thing the recipe does. Cooking the garlic a little harder releases considerable flavor for the later steps, too.

C) If you refrigerate the marinara in its base form, you can add pre-cooked meatballs and/or sausage and/or mushrooms during any later re-heat(s); just make sure to give it another four hours at 150°F to 160°F for the marinara to deliciously invade the new ingredients.

D) In the image, the burner is set to 220°F. This does not cause the marinara to simmer. The burner in question displays an average temperature. It actually applies higher temperature pulses, with intervening periods of no heat applied. Although the metal bottom of the double boiler is hot enough to make steam, because of all the metal in the two sections of the double boiler and the mass of water in the bottom section distributing that heat, there's quite a bit of heat dissipation in the water and the metal before the remainder of the heat is applied to the top section. All the bottom of the double boiler does is steam very gently. The marinara in the top section is cooler yet, again, because that heat is distributed even further. So no, I'm not countering my own advice and simmering the marinara.

E) Note the lack of (much) salt and any pepper. Add these when the marinara is actually served over your pasta; this is a much more effective way to enhance the marinara and it allows each person at the table to season according to taste.