In a medium bowl, cover chiles with boiling water. Let stand until softened, 15 minutes. Drain, stem, and seed chiles, then transfer to a blender with onion, garlic, and water. Puree until smooth. Season with salt and pepper. Pour through a fine-mesh sieve and discard solids. In a medium pot, heat oil over high until shimmering. Add chile mixture, raisins, and broth and simmer, stirring occasionally, until thickened, 5 to 10 minutes. Remove from heat and stir in vinegar and sugar. Season to taste with salt and pepper.
Refrigerate in an airtight container, up to 4 days.