Put the raisins, sugar, tamarind pulp, 1/2 cup water, Garam Masala, ginger, chile and onions into a medium saucepan and place over medium-high heat. Bring to a boil, and then reduce the heat to low and simmer gently for 45 minutes to 1 hour. Let cool slightly, and then stir in the cilantro.
Preheat the oven to 325 degrees F.
Put the coriander seeds, cumin seeds, peppercorns, cardamom pods, cloves and cinnamon sticks on a baking sheet and toast in the oven until they are aromatic, 15 to 20 minutes. Grind to a powder in an electric spice grinder. Store in an airtight jar.