- 1/2 teaspoon vegetable oil
- 1 apple, peeled, cored and chopped
- 2 tablespoons brown sugar
- 1 cup apple cider vinegar
- 2 tablespoons yellow mustard
- 1 tablespoon red pepper flakes, or to taste
- 1 tablespoon ground black pepper, or to taste
- Heat oil in a saucepan over medium heat. Place apple pieces in saucepan; cook and stir until they are slightly caramelized, about 2 minutes.
- Stir brown sugar into apples; cook, stirring constantly, until the mixture starts to bubble, about 2 minutes.
- Pour apple cider vinegar into saucepan. Reduce heat to low and cover. Cook until the apples are soft and falling apart, about 30 minutes. Remove from heat.
- Whisk in mustard, red pepper flakes, and black pepper.
- Transfer mixture to blender and puree until completely smooth.