Late Summer Greens Saute

From Bon Appetit. My husband and I have been eating this 2 - 3 times per week since I began fixing them this way. We love them!

• Ready In: 1 hr
• Serves: 8

Ingredients

• 1⁄4 cup extra virgin olive oil
• 1  cup shallots or 1  cup sweet onion, thinly sliced
• 2  garlic cloves, crushed
• 1  teaspoon crushed red pepper flakes
• 1 3⁄4 lbs  assorted greens, stems removed and thinly sliced, leaves chopped (such as kale and Swiss chard)
• 1⁄4 cup apple cider vinegar
• 3  tablespoons unsalted butter
•  kosher salt, freshly ground pepper

Directions

1. Heat oil in a large heavy pot over medium heat. Add shallots and garlic. Cook, stirring often, until soft, about 5 minutes.
2. Add red pepper flakes; stir 1 minute. Add kale stems; sauté for 4 minutes. Add leaves and cook, tossing often, until crisp-tender, about 5 minutes.
3. Stir in vinegar. Add butter; toss until melted. Season with salt and pepper.