1 cup chicken stock
2 tablespoons red-wine vinegar
2 tablespoons marmalade
1 teaspoon Dijon mustard
1 teaspoon cornstarch
1 pound chicken tenders
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground pepper
2 tablespoons butter
1 medium white onion, chopped
1 teaspoon freshly grated orange zest
First whisk stock, vinegar, marmalade, mustard and cornstarch in a medium bowl.
Season chicken with salt and pepper. Heat 1 tablespoon butter in a large skillet over medium-high heat. Add the chicken and cook until golden, about 2 minutes per side. Remove to a plate.
Add the remaining butter, then the onions to the pan and cook, 30 seconds. Whisk the broth mixture and add it to the pan. Bring to a simmer, scraping up any browned bits. Reduce heat to maintain a simmer; cook until the sauce thickens, about a minute. Add the chicken and return to a simmer. Cook, turning once, until the chicken is heated through, about 1 minute. Remove from the heat and stir in orange zest.