In this satisfying salad, bacon and lemon juice balance the slight bitterness of chicory and frisee.
Place the bacon in a large skillet over medium heat. Cook until it is golden and crisp. Drain on paper towels. Break into 1- to 1 1/2-inch pieces; set aside. Drain all but 1 1/2 tablespoons bacon fat from the pan. Add the onion. Cook over medium heat until soft and golden, about 5 minutes. Remove from heat.
Place the chicory, frisee, bacon, and onion in a large bowl. In another bowl, whisk the lemon juice, olive oil, salt, and pepper. Drizzle over salad, and toss. Serve the salad immediately.