- 5 tablespoons olive oil
- ¼ cup drained capers, patted dry
- 2 pounds Brussels sprouts, thinly sliced
- ½ red onion, thinly sliced
- Kosher salt and black pepper
- 8 cups baby kale (5 ounces)
- ¼ cup fresh lemon juice
- 1 fresh long red pepper, thinly sliced
- ½ cup freshly grated Parmesan, plus more for garnishing
- Heat 1 tablespoon of the oil in a large skillet. Add the capers and cook over moderate heat, stirring, until golden and crisp, 1 to 2 minutes. Transfer the capers to a paper towel–lined plate.
- Add 2 tablespoons of the oil, half the Brussels sprouts, and half the onion to the skillet. Season with ½ teaspoon salt and ⅛ teaspoon black pepper. Cook over moderate heat, stirring, until crisp-tender, about 5 minutes. Transfer to a large plate. Repeat with the remaining 2 tablespoons of oil, Brussels sprouts, and onion.
- Return all the Brussels sprouts to the skillet and stir in the kale, lemon juice, red pepper, and Parmesan. Season with ½ teaspoon salt and stir to combine. Transfer to a serving platter and garnish with the capers and more Parmesan.
- Serve warm or at room temperature.
Make-Ahead: Slice the vegetables and refrigerate in airtight containers for up to 2 days.