Donna Fales

Ingredients

• 6 tablespoons (3/4 stick) chilled butter
• 3 tablespoons vegetable oil
• 1 large red onion, halved lengthwise, thinly sliced crosswise
• 1/2 yellow onion, thinly sliced
• 1 1/2 tablespoons sugar
• 3/4 cup Sherry wine vinegar
• 1 tablespoon coarse kosher salt
• 2 teaspoons ground cumin
• 1/4 teaspoon ground black pepper
• 6 boneless chicken breast halves with skin
• 4 teaspoons olive oil