How to Make It
Preheat the oven to 500°. On a rimmed baking sheet, spread the tomatillos, beefsteak tomato, serranos, pasilla, onion and garlic. Roast the vegetables in the center of the oven for about 15 minutes, turning them once or twice, until softened and lightly browned in spots.
Peel and core the beefsteak tomato and cut the flesh into quarters. Crumble the pasilla chile into a blender or food processor and add the remaining roasted vegetables and any juices. Add the cilantro sprigs and lime juice and puree until smooth. Season the salsa with salt.
The tomatillo-cilantro salsa can be refrigerated overnight.
Dried pasilla chiles are available at Latin American markets, specialty food stores and some supermarkets.