Silky Salsa Verde - Alton Brown

Ingredients

• 1 pound tomatillos, husks removed and rinsed
• 1 serrano chile, stemmed, halved and seeded
• 1/2 large white onion, peeled and separated
• 1 1/2 teaspoons grapeseed oil
• 1 cup packed fresh cilantro with stems
• 1 1/2 teaspoons kosher salt
• 1/4 teaspoon xanthan gum