Preheat oven to 425°. Combine 1 chipotle chile in adobo, finely chopped, 4 Tbsp. adobo sauce, 1 tsp. honey, 2 Tbsp. extra-virgin olive oil, 1½ tsp. ground cumin, and 1½ tsp. Diamond Crystal or ¾ tsp. Morton kosher salt in a large bowl. Squeeze juice from 1 small lime into bowl and stir to combine. Add 4 skinless, boneless chicken breasts and turn to coat. Let sit 10 minutes.
Place 1 large red onion, halved, cut through root end into 1½”-thick strips, on a rimmed baking sheet; drizzle with oil and season with kosher salt. Toss to coat. Arrange in an even layer, then nestle chicken among onion. Roast until chicken is cooked through and onion is tender, 22–25 minutes. Transfer chicken to a cutting board and slice.
Meanwhile, place ¼ cup raw pumpkin seeds (pepitas) on a small baking sheet. Drizzle with a little oil, season with kosher salt, and sprinkle with a pinch of ground cumin. Toss to coat, then spread pumpkin seeds out into an even layer. Roast until golden brown, about 5 minutes.
Place 1 bunch kale, ribs and stems removed, leaves thinly sliced, in a large bowl. Cut 1 avocado in half; remove pit and discard. Scoop flesh into bowl. Squeeze juice of 1½ small limes over kale and drizzle generously with oil; season with kosher salt. Using your hands, squeeze and mash avocado, massaging into kale to soften slightly. Mound salad on a platter.
Thinly slice remaining 1 avocado. Top salad with chicken, avocado, and roasted onion as desired. Scatter pumpkin seeds on top. Squeeze juice of remaining ½ small lime over entire salad; sprinkle with flaky sea salt.