Sprinkle the steak with salt and set aside. Add a few tablespoons of olive oil to coat the bottom of a large stock pot. Brown the steak tips over high heat, about 5 minutes. Then remove from the pan and set aside.
Bring to a boil and then turn down to medium heat and let simmer for 1½ hours. At that point add the mushrooms. Stir to combine and then cook for another 30 minutes.
Once finished cooking, add the spinach. Stir to combine and then serve.
Recipe by Autoimmune Wellness at https://autoimmunewellness.com/steak-mushroom-and-onion-soup/