Heat the oil in a 10-inch skillet over medium-high heat. Add the chicken and cook until well browned on both sides.
Add the onions to the skillet and cook for 2 minutes, stirring occasionally. Stir in the rum. Cook and stir for 2 minutes, scraping up the browned bits from the bottom of the skillet.
Stir in the picante sauce and syrup and heat to a boil. Reduce the heat to low. Cook for 10 minutes or until the chicken is cooked through. Slice the chicken before serving.