In a bowl, whisk the vinegar, salt, pepper and Dijon mustard until completely blended. Slowly add the Olive Oil, whisking constantly until completely incorporated. May be refrigerated for up to 5 days.
Arrange the greens on a serving plate, and add the tomato and onion. Top with freshly grated cheese, then place a scoop of diced pears on top of the salad. Chill until ready to serve.
When ready to serve: Shake or whisk the vinaigrette and pour 2 or 3 tablespoons over the pears and greens. Sprinkle salad with a pinch of cinnamon, if desired.
