Cut the sausage into bite-size pieces, leaving the casing on or removing it if prefered. Cut the cabbage into 2" chunks. Cut the other vegetables into 1-2" pieces. Measure the spices and liquids.
Sauté and Deglaze
Add butter or oil to inner pot of Ninja Foodi or pot on stove. Heat on high sear/sauté until the butter begins to melt. Add in the sausage pieces and start to brown them.
Add in the cabbage and toss everything around for a few minutes to get some browning on the cabbage leaves. Sauté over high heat for about 5 minutes.
Add in the chopped carrots, celery, and onion. Stir. Deglaze the pot with the chicken broth and scrape the bottom of the pot to remove anything that might be stuck on.
Pressure Cook
Add the tomatoes with the juice on top. Add the chopped red peppers if using. Put the pressure lid on and turn the valve to seal. Pressure Cook on high for 2 minutes and when the time is up, allow the pot the natural release the pressure for 10 minutes. Then, manually release the remaining pressure.
Remove the lid and stir. Check the broth for seasonings and add more seasonings if desired. Serve & Enjoy.
Stovetop
Add in the tomatoes with juice and the chopped red peppers and stir everything together. I would also add another cup of chicken broth since you will have some evaporation during the simmering time. You can add this anytime so it's fine to wait until closer to the end of the simmer time.
Bring the contents of the pot to a boil and then reduce your heat until the soup is simmering. Simmer for 25-30 minutes or until the cabbage has reached your desired texture and the sausage is fully cooked.
Taste the broth for seasonings and add more seasoning if desired.