Easy French Onion Appetizer

1 round puff pastry thawed
2-3 small yellow onions sliced very thin
1/2 cup grated gruyere cheese
2-3 sprigs of fresh thyme
See Salt Fleur de Sel + Pepper

Preheat oven to 375º. On a round sheet pan roll out the puff pastry. Spread the cheese into a thin layer on the pastry leaving 2 inches around the edge. Cover the cheese with thinly sliced onions making sure no to overlap the onions too much so they will cook evenly. Strip the thyme leaves from a couple of stems of thyme and sprinkle over the onions. Sprinkle a good pinch of Fleur de Sel + Pepper over the top. Fold up the 2 inch edge of the pastry over the top of the onions. Bake for 35-40 minutes until the pastry is golden and the onions are cooked through. Serve right away.