Preheat oven to 425 degrees.
In a large skillet, heat 2 tablespoon olive oil and stir in sliced onions and kosher salt. Cook and stir over medium heat until onions are starting to soften and become golden- about 5 minutes- and stir in asparagus.
Continue to cook vegetable mixture for 5-7 minutes longer. The asparagus should be bright green and tender, the onions golden brown and caramelized. Remove from the heat.
Place the flat bread rounds on a lined baking sheets (you'll need two) and spread each with 3 tablespoon of pesto, followed by a ¼ C of mozzarella cheese.
Arrange potato slices over the cheese and divide and spread the vegetable mixture evenly over the tops of each flat bread.
Top each completed flat bread with 2 tablespoon of parmesan cheese and drizzle with 1 tablespoon of olive oil.
Place in the oven and bake for about 10-15 minutes or until the bread is nicely browned and cheese is melted.