Preheat oven to 375 degrees
Combine vinegars and garlic to make marinade
Pierce filet mignon with knife in several places and on both sides - place in marinade turning to coat
Let rest in marinade about 20 minutes, turning halfway through
Preheat skillet - remove filet mignon from marinade and sprinkle with Steakhouse seasoning and rosemary
Brown filet mignon on all sides
Remove filet mignon from skillet and turn off burner - place on foil covered baking sheet and put in preheated oven
Add broth to skillet scraping to pick up any burned bits (deglaze)
Add 2 teaspoons of the marinade, the sliced onions and the Roasted Garlic seasoning
Stir to combine the broth and seasonings with the onion
Bring onions to a boil and then reduce heat to medium low cooking until onions are translucent and most of the liquid is gone
Remove filet mignon from oven when desired doneness is reached and let rest for 5 minutes
Slice filet, and top with caramelized garlic onions