Heat the oil in a large skillet over medium heat. Add the onion and a pinch of salt and cook, stirring occasionally, for 5 minutes or until softened. Add the spinach and cook, tossing, for one minute or until slightly wilted. Transfer to a serving bowl and drizzle with balsamic.
Add the pecans to the pan and set over high heat. Toast for one minute. Chop. Add nuts and cheese to the salad and toss to combine. Season with freshly cracked black pepper.