Roasted Tomatillo and Avocado Salsa

Name: Roasted Tomatillo and Avocado Salsa
Ingredients: 1 large onion, quartered; 2 jalapeños, halved lengthwise, ribs and seeds removed if desired; 1 poblano chile, halved lengthwise, ribs and seeds removed; 8 oz. tomatillos (about 5 medium), husks removed, rinsed, halved, quartered if large; 2 Tbsp. extra-virgin olive oil; 2 tsp. Diamond Crystal or 1¼ tsp. Morton kosher salt, plus more; 2 medium ripe avocados, coarsely chopped; 1 garlic clove, coarsely chopped; ⅓ cup coarsely chopped cilantro; 6 Tbsp. fresh lime juice; Plantain chips (for serving)