Get egg to 400 degrees.

Roll out the puff pastry.

Fold the edges to create a little wall.

Using a fork poke small holes in the center(docking)

Now in a med high skillet begin to caramelize the onions(about 15-20 mins) in a combination of butter and oil

When the onions are caramelized some of them in the center of the tart.

Place on a cold pizza stone dusted with corn meal.

When about 3/4 way done top with blue cheese and finish cooking.

Cut and serve