Slice the steak into as thin of slices as possible.
Melt the butter in a large skillet and add the slices of meat.
Thinly slice the onion and add to the pan.
Cook for 5-7 minutes until the meat has started to brown and the onions are translucent.
Thinly slice the mushrooms and add them to the pan with the meat.
Season with garlic powder, salt, pepper and tarragon.
Add the beef broth and bring to a simmer over medium low heat.
Simmer for about 25 minutes until the meat is tender and the mushrooms have softened.
While the meat is cooking, cut the cauliflower into florets and steam until tender.
Remove the meat from the heat and stir in sour cream, if using, stirring until well incorporated.
Serve atop the steamed cauliflower and enjoy!
For a more tender stroganoff, simmer in the pan, covered, for an additional 30 minutes on medium/low heat before adding the sour cream.Alternatively, make cauliflower mashed potatoes to serve your stroganoff over.