Step 1

Preheat the oven to 375 degrees F.

Step 2

Heat a skillet over medium-high heat. Add the olive oil and onions to the pan and reduce the heat to medium. Cook, stirring often with a wooden spoon, until the onions are a dark golden-brown, about 30 minutes. Season with the kosher salt. Stir in the balsamic and fresh oregano and remove from the heat to cool slightly.

Step 3

Sprinkle the cornmeal evenly on a nonstick, rimmed baking sheet. Unroll the pie crust over the corn meal and press gently so the corn meal sticks to the bottom of the pie crust. Crumble half of the goat cheese over the crust, leaving about a 2-inch border. Add the caramelized onions and spread them evenly over the crust still keeping the border. Fold the border edges up and over the edge of the filling, crimping every 2 inches or so. Crumble the remaining cheese over the top of the exposed onions. Place the tray in the preheated oven and bake until the crust is golden brown and the cheese is melted, about 30 minutes. Allow the tart to cool for 10 minutes on the tray.

Step 4

Meanwhile, in a small bowl, dress the arugula with the lemon juice. Sprinkle the arugula over the warm crostata. Slice into wedges or squares and serve.