Have all your can's opened and ready to go. This entire recipe will fit in a 6 quart pot. Add olive oil to your Instant Pot, press sauté and set for ten minutes. When the oil is hot, add the chopped onion and sauté until soft. (Or use a stainless or non-reactive Dutch oven.)
Add the garlic and tomato paste and continue stirring until the tomato paste starts to cook and darken. Stir constantly until fragrant. About a minute.
Deglaze the pan with wine, chicken broth or some juice from the tomatoes and scrape the bottom of the pot to lift up any browned bits.
Stir in four cans of tomatoes. Use a little broth to get the bits out of the bottoms of the cans and add the entire can of broth.
Add 1 bag/box of spinach and press down into the soup.
Add the entire bag of meatballs and press down into the soup. If using a pressure cooker, be careful to make absolutely sure not to go over the fill line!
Add a parmesan cheese rind if you have one. Trust me, this adds a ton or flavor.
Add one more bag/box of spinach. Press down if possible. Remember, if you are using the Instant Pot, be careful to make absolutely sure not to go over the fill line!
Place lid on Instant Pot and set the valve to sealed position. Pressure cook for 12 minutes on high pressure. (Or simmer stirring frequently and gently for at least 1 hour on the stove or until tomatoes are cooked through and soup has reduced slightly. If you cook on the stovetop, you may need to add another can of broth.)
When the timer goes off, wait five minutes, turn off Instant pot and do a quick release.
Stir gently. Taste and adjust for salt and pepper.
If the tomatoes are acidic, add a tiny pinch or about 1/8 tsp of baking soda and stir ->only use a tiny pinch.
Turn Instant Pot on sauté for 30 minutes. Add in the final 2 bags/boxes of spinach. Periodically stir it gently.
Serve 3 meatballs per person with the spinach and tomatoes. Top it off with a generous tablespoon of fresh grated or shredded parmesan cheese!