Upside Down Onion Tarts

Preheat oven to 400 degrees F and line 2 baking sheets with parchment paper.
Slice pastry dough into squares (for my dough I cut each sheet into 6 squares). Set aside.
Make 6 small pools of olive oil on each prepared baking sheet, 12 in total. Add a drizzle of balsamic glaze to each pool.
Place an onion slice on top of each pool, then season with garlic powder, salt, and pepper.
Top each onion with a slice of swiss and grated parmesan and then a square of pastry dough, crimping down edges so dough full covers the cheese.
Brush dough with egg white.
Bake tarts for 12-15 minutes or until golden brown.
Allow tarts to cool for at least 5 minutes before flipping for best results. Drizzle additional balsamic glaze on top if desired.