Turn the Instant Pot to saute, add in the oil, and let it heat for 1-2 minutes. Once heated, add the onions, carrots, and celery to the Instant pot. Let saute for 2-3 minutes, or until the onions begin to soften. Add in the garlic and oregano. Saute that for 1 minute.
Add in dry red wine (or additional broth) and scrape up any browned bits from the bottom of the inner pot and let cook off for 1-2 minutes. Turn the saute function off.
Add the vegetable stock, marinara, zucchini, beans, elbow noodles, bay leaf, salt, and stir well.
Place the lid on the Instant Pot and set cook time for 1 minute on high pressure.
Once the cooking time has been released, let the pressure release naturally for 10 minutes. After 10 minutes, do a quick release of the remaining pressure by using a wooden spoon to hit the vent knob from sealing to venting. (Be sure to stand away from the vent knob to protect yourself.)
Remove the bay leaf and then stir in the spinach and red wine vinegar. Place the lid back on the pressure cooker and allow the spinach to wilt for just a couple of minutes.
Serve the soup with freshly grated Parmesan if desired.
Wine: the dry red wine is optional but adds incredible flavor. Use a dry wine such as merlot or cabernet and be sure it is suitable for drinking. Don't use a wine labeled cooking wine, as the flavor is not very good!Beans: I use kidney beans and Great Northern beans, but you can use all kidney beans, white beans, or even garbanzo beans/chickpeas work great in Minestrone.Noodles: For the noodles, elbow noodles are traditional, but orecchiette or small shells are a great substitute. Whole wheat or regular noodles work perfectly.Gluten-Free Modifications: For gluten-free noodles, I recommend Barilla Gluten Free--those are the only noodles that cook up well in the soup without releasing too much starch.Spinach: Feel free to stir in baby kale instead of the kale. You can also add shredded cabbage BEFORE pressure cooking if desired. Storage: Leftover minestrone soup can be stored in a sealed container for up to 5 days in the refrigerator. It also can be frozen for up to 3 months. Keep in mind you may need to add a bit of stock when reheating, as the noodles will absorb the extra broth.