Balsamic reduction:

Place balsamic in a small saute pan. Turn heat to medium high. Let simmer until reduced and noticeably thick. 

Preheat oven to 500F. Line a sheetpan with parchment paper or grease lightly with olive oil. Place rolled out dough onto pan and drizzle with olive oil.

Cover the dough with a layer of cheese. Arrange one layer of sliced nectarines on top of the cheese. Sprinkle with fruit layer with fresh parmesan. Place pizza in oven and baked for 10 minutes until the crust in slightly brown and cheese in melting. 

Remove from oven and sprinkle with bail. Drizze reduced balsamic. Slice and serve