Preheat frying pan over medium heat.
Add butter or oil and onion; reduce heat to low.
Sauté for 10 minutes, stirring frequently.
Add peaches, and sauté for 2 more minutes.
Add apple cider vinegar, water, and brown sugar, stirring to combine.
Increase heat to medium.
Continue to stir regularly for approximately 2 minutes until all the liquid has been absorbed.
Remove from heat, and sprinkle with cinnamon, stir well.
Serve with crostini and goat cheese.