1. Remove the zest from half the lemon with a vegetable peeler. Repeat with half of the orange. Cut the zest into very thin slivers. Bring a small pan of water to a boil. Add the zest strips and cook for 5 minutes. Drain in a wire sieve and rinse under cold running water.

2. Squeeze the juice from the lemon and orange. Stir the lemon juice, orange juice, mustard, cayenne, and salt in a small saucepan until the salt dissolves. Add the port and jelly and bring to a boil over medium heat. Simmer over low heat for 5 minutes.

3. Strain the sauce through a wire sieve into a serving bowl and stir in the citrus zests. Serve hot, warm, or at room temperature.

Variation

Spicy Cumberland Sauce

For a slightly spicier version, add an extra pinch of cayenne pepper and a pinch each of ground cloves and ground ginger.