1 medium red onion, halved and thinly sliced lengthwise
1¼ teaspoons salt, divided, plus extra for serving if needed
1¼ cups halved seedless red grapes
1½ bunches Lacinato kale (about 6 ounces)--stems removed, leaves stacked, rolled and sliced crosswise into wide ribbons
Directions
In a small bowl, whisk together 1 tablespoon of the olive oil with the balsamic vinegar and the red pepper flakes. Set aside.
In a large skillet set over medium-high heat, add the remaining 1 tablespoon of olive oil. Add the onion and ½ teaspoon salt and cook, stirring often, until the onion is brown and frizzled around the edges, about 4 minutes. Add the grapes and cook until browned, about 2 minutes.
Pour the oil-balsamic mixture into the pan and immediately add the kale. Use tongs to stir and turn the kale into the onion-grape mixture. Once the kale starts to wilt, after about 1 minute, turn off the heat and transfer the kale mixture to a serving bowl. Taste and season with the remaining ¾ teaspoon of salt. Serve warm or at room temperature.