1/2 cup onion, minced
1 cup mustard, yellow
1/2 cup lemon juice, ideally fresh
1 tsp celery seeds
1/4 cup white vinegar
1/4 cup dark brown sugar
2 tablespoons vegetable oil
1 tsp salt
Heat the oil in a medium-size saucepan over medium heat.
Add the onions and sauté until translucent for about 3 to 4 minutes.
Add the rest of the ingredients, and mix them well.
Bring to a boil, then reduce the heat and simmer 20 minutes.