Sauté onion slices in hot oil in a medium skillet over medium heat 6 minutes or until tender and golden brown. Add pecans, and cook 2 minutes or until pecans are lightly toasted. Stir in vinegar and honey; remove from heat. Toss together salad greens and warm onion mixture in a large salad bowl just until greens are thoroughly warmed. Sprinkle with salt and pepper to taste.