A favorite brie appetizer

I made this appetizer for New Year's Eve because it's one of my favorites. I just realized I blogged about it a couple of years ago, but oh well, I like it! Since I've made it many times, I've got a bunch of tips:
- If your dried cranberries seem a little dry or shriveled, put them in a bowl and pour some boiling water on top. Let them sit for three minutes or so and drain. They'll soften right up.
- If you want to make this ahead, put the onion mixture in a bowl and refrigerate until ready to serve. Bake the Brie for 8 minutes, put on the topping, then bake for another 3 minutes or so. I once put the brie and topping in the oven at the same time. The cranberries became hard, black little turds -- which is why I've started soaking them as insurance.
- You can heat it in the microwave. First heat the brie for a couple of minutes, then the topping for about 30 seconds, then put the topping on top of the brie.

Brie with Caramelized Onions, Pistachio and Cranberry

2 tablespoons butter
1 medium onion, cut into fourths and thinly sliced
1/2 cup dried cranberries
1 tablespoon brown sugar
1 tablespoon balsamic vinegar
Vegetable oil or cooking spray
1 round (15 ounces) brie
1/4 cup coarsely chopped pistachio nuts
Crackers and/or sliced Italian bread

Preheat oven to 350 degrees. Melt butter in 10-inch skillet over medium heat. Cook onion in butter for 10 minutes, stirring frequently. Stir in cranberries, brown sugar, and vinegar. Cook about 5 minutes, stirring frequently, until mixture is thickened, brown, and caramelized.

Scrape the top rind off of the brie. Lightly brush oven-proof plate with oil (or spray with cooking spray) and place cheese in the center. Bake uncovered 8 to 10 minutes or until cheese is soft and partly melted. Spoon onion topping over cheese. Sprinkle with nuts. Serve with crackers.