Combine the roasted poblanos, minced ginger, cumin seeds, cilantro, and asafetida (if using) in a high-speed blender or food processor.
Purée the mixture until completely smooth. If needed, add a tablespoon or two of water to help it blend.
Place a medium saucepan over medium-high heat and add the oil.
Once the oil is hot and shimmering, carefully pour in the chile purée. Be cautious, as it will splatter when it hits the hot oil.
Cook for 2 minutes, stirring frequently.
Reduce the heat to low and let it simmer, stirring occasionally, until the sauce has thickened slightly, about 2 to 3 more minutes.
Remove the pan from the heat.
Season to taste with salt and pepper, then stir in the fresh lime juice.
Serve hot, or allow it to cool and store in an airtight container in the refrigerator for up to 3 days.
