To a sauté pan over medium heat add the olive oil. Add the butter to the pan, then add the onions.
Cook the onions until they start to brown, about 30 minutes, stirring every 5 minutes. Add a pinch of salt and stir. When they start to brown, removed from the heat and set aside.
Preheat oven to 500°F/260°C. Line a large baking sheet with parchment paper.
Place the dough onto a lightly floured surface. Use your hands to shape into a rectangle. You can also make it round. Place the dough onto the baking sheet, brush with olive oil and bake for 5 minutes until it starts to turn brown (you don’t want it brown yet). If parts bubble up, don’t worry, they will flatten when you remove from the oven. If you’re using a dark pan, it will cook faster.
Remove from the oven and add the toppings: grated cheese, onions, apples and bacon.
Return to the oven and bake until the cheese is melted, about 8-10 minutes. Again, it will be faster if using a darker pan.
Top with chopped Italian parsley (optional), slice and serve.