- 1 large navel orange
- 2/3 cup sugar
- 1/2 cup kumquats, sliced
- 1/2 teaspoon crushed red pepper flakes
- 1/4 teaspoon coarsely ground black pepper
- 2 tablespoons fresh orange juice
- Using a knife, remove peel from orange. Set orange aside. Cut white pith from peel. Place peel in a medium saucepan and add cold water to cover by 1″. Bring to a boil; drain. Repeat 2 more times. Let cool slightly.
- Finely chop peel and reserved orange; place in a medium saucepan and add sugar, kumquats, both peppers, and 2 cups water. Bring to a boil, reduce heat, and simmer, stirring occasionally, until water is evaporated, 35–45 minutes. Let cool; mix in orange juice.
- DO AHEAD: Marmalade can be made 2 weeks ahead. Cover and chill.