Caramelizing the onions is easy, but it takes about 45 minutes of frequent stirring. Cut your onion in half, and then slice each half into thin thin slices. Add the slices to a pan on medium low heat with butter, olive oil, and 1/4 teaspoon of sea salt. Stir frequently for about 45 minutes until onions are a deep golden color.
Cut the rind off of your brie and add the brie to a small oven safe baking dish
Once the onions are done caramelizing, add the onions on top of the brie, followed by 1/2 cup shredded cheese, the seasoning salt, and garlic powder.
Preheat your oven to 400F
Cook for 5 minutes and remove from the oven so that you can mix the brie and onions around.
Once it is well mixed, add remaining shredded cheese on top and add it back to the oven. Cook for an additional 15-20 minutes or until the top is bubbly and light golden brown.