½medium-size head radicchio, halved again through the core, then thinly sliced crosswise
Coarse kosher salt and freshly ground pepper
Splash of Sherry wine vinegar
Instructions
Heat the oil in a large nonstick skillet over medium-high heat. Add the onion and pepper flakes and sauté until the onion begins to soften, about 3 minutes. Add the sliced radicchio, sprinkle with salt and pepper and sauté until beginning to soften, about 3 minutes. Remove from the heat. Add a splash of vinegar and stir. Season to taste with salt and pepper.