1. Heat oven to 425 degrees F. Unfold puff pastry onto a baking sheet. Fold all edges over 1/2 inch to form border. Prick center of dough with fork. Bake at 425 degrees F for 15 minutes.
2. Meanwhile, melt unsalted butter in a large skillet. Add onions; cook over medium heat for 5 minutes. Sprinkle with ground cumin, sugar and salt. Cook 6 more minutes or until golden and fragrant.
3. Once crust is baked, sprinkle with shredded Monterey Jack cheese. Top with onions; return to oven. Bake at 425 degrees F for 5 minutes. Cut in squares and serve.