This can be served on a wedge of pita bread and garnished with yogurt and cilantro.
Remove cardamom seeds from pods and grind with mustard seeds in a spice grinder or with a mortar and pestle. In a large nonstick skillet, heat oil over high heat. Add ground cardamom and mustard, bay leaves, pepper flakes, sugar, and ginger, and stir until mixture darkens slightly, 1 to 2 minutes. Stir in onions, broth or water, and salt. Reduce heat to a simmer; cook for 10 minutes, stirring occasionally. Stir in tomatoes and cook for 40 minutes longer, or until onions are soft and flavors are well blended. Stir in vinegar.
Warm pita breads in a 250-degree oven and cut into wedges. Place marmalade in a serving dish, and serve with pita wedges and bowls of yogurt and chopped cilantro.
Toasting the spices heightens their flavors;stir constantly to prevent burning.