Melt butter in a cast iron Dutch oven (stew pot) over medium heat. When the butter is melted, add sliced onions and sauté for 15 - 20 minutes, stirring often, until onions turn golden brown.
Add remaining ingredients (but not the garnish) to the pan and stir to combine. Heat soup until it's boiling, then reduce heat and simmer covered for 1 hour and then uncovered for additional 20 minutes. Season as needed.
Make croutons for the top of the soup by slicing gluten free / sourdough focaccia bread into 3/4-inch thick slices. Butter both sides of those slices, then cut the slices into bite-size cubes.
Bake the bread in a 425-degree oven for 15 minutes or until crispy. Shave the cheeses by simply dragging a potato peeler over the edge of the wedge.
Serve the soup hot with a handful of croutons floating on top followed by a couple tablespoons of shaved cheeses.
Enjoy!
Keyword bay, bone broth, butter, classic french onion soup, creamy tortellini soup, flour, garlic, onion, recipes, thyme, white wine vinegar