Heat a skillet over medium heat and add the bacon. Cook, stirring often, just until the fat is rendered - you do not want to cook it until crispy, because it will crisp up more in the oven. Remove the bacon with a slotted spoon and place it on a paper towel to remove excess grease.
Throw the onions into the skillet with the rendered bacon fat. Add a pinch of salt and pepper. Cook, stirring often, for 10 minutes until the onions begin to soften. Reduce the heat to low. Stir in the apple cider. Cook for another 15 to 20 minutes, stirring often, until the onions are slightly caramelized. This will start to happen quicker after you add the apple cider.
Preheat the oven to 425 degrees F. Place the sheet of puff pastry on a baking sheet lined with parchment paper. Poke it all over with a fork.
Stir the ricotta and pumpkin together in a bowl until combined. Spread it all over the sheet of puff pastry, leaving a one inch border.
Top with the mozzarella, caramelized onions, bacon and fresh sage. Brush the edges of the pastry with the egg wash.
Bake for 20 to 25 minutes, until the crust is golden and crisp on the edges. Sprinkle with parmesan. Let cool slightly before serving!