1 bunch kale, tough inner stems discarded, leaves roughly torn (about 1 pound)
2 tablespoons olive oil
Kosher salt
1 small red onion, thinly sliced
1 teaspoon dried ground sumac berries
1/2 teaspoon toasted sesame seeds
1 tablespoon juice from 1 lemon
1 clove garlic, grated on a microplane grater
2 teaspoons dijon mustard
1 (14-ounce) can chickpeas or white beans, drained and rinsed
Freshly ground black pepper