Add the butter and two tablespoons of olive oil to a large skillet set on medium-low heat.
Cook the sliced onions for about 30 minutes. Stir in the sliced mushrooms, continuing to saute for an additional 4 minutes.
Add the seasoning in a ziploc bag. Shake to mix well.
Add the sirloin strips in the ziploc bag filled with the mixed seasonings.
Shake to coat the meat with the seasonings.
Cook on medium heat for 5-10 minutes.
Prepare to serve by opening the pita bread and assemble with the steak, onions, and mushrooms. Add diced cucumbers and sliced cherry tomatoes.
Add the dried oregano, basil, garlic powder, marjoram, parsley flakes, rosemary, and thyme in a ziploc bag. Shake to mix the seasonings.
Add the thin strips of sirloin steak to the bag. Shake the bag to coat the steak with the seasonings.
Add one tablespoon of oil to the skillet cooking on medium high heat.
Reshake the seasoning bag again to ensure that the steak slices have been well coated.
Cook the sirloin steak slices in small patches for 1-2 minutes per side.
Remove the steak after it has cooked and add in the sliced mushrooms.
Prepare to serve by opening the pita bread and assemble with the steak, onions, and mushrooms. Add some of the diced cucumbers and sliced cherry tomatoes.
Serve and enjoy!.