Heat a dry skillet over medium-high until hot. Add coriander and cumin seeds and cook, swirling pan occasionally, until fragrant and toasted, about 1 minute. Let cool, then grind in a spice grinder or mortar and pestle.
Heat oil in a large pot over medium heat. Add onions and saute until translucent and tender, stirring occasionally, about 10 minutes. Add garlic, 1 teaspoon salt, 1/2 teaspoon pepper, spices, molasses, and brown sugar; stir to combine. Cook, stirring frequently, 3 minutes. Add tomatoes, reserved juice, and cider vinegar and bring to a simmer. Reduce heat to medium-low and simmer gently, stirring occasionally, until mixture is thick and dark, about 1 hour.
Let cool slightly then puree sauce in a blender. Add white vinegar and Worcestershire; puree until smooth. Season to taste with additional salt, pepper, and white vinegar. Sauce can be refrigerated up to 3 days in an airtight container; let cool completely before storing, and reheat over medium before serving.