In a medium saucepan, cook onion in oil over medium heat until soft, 5 minutes. Stir in salt, chili powder, dry mustard, pepper, chile flakes, and cumin. Cook until seasonings are fragrant, 1 to 2 minutes. Add tomatoes, vinegar, sugar, and molasses. Simmer, covered, stirring occasionally, for 1 hour.
Add berries and simmer gently, uncovered, until softened, 25 minutes. Purée most of sauce in a blender, then stir into remaining sauce.
*Buy from specialty produce markets or nwwildfoods.com, or pick your own in the wild from August through October.