In a frying pan over medium heat, add the olive oil and sliced onions. Cook the onions until they are caramelized, about 10–15 minutes.
Preheat your oven to 350°F (175°C).
In a large mixing bowl, whisk together the eggs and heavy cream. Season with salt and pepper to taste.
Place the caramelized onions into a casserole dish. Add crumbled bacon and half of the cheese. Pour the egg mixture over and top with the remaining cheese.
Bake in the preheated oven for 25–30 minutes, until the top is golden and firm.
Notes
Store leftovers in an airtight container in the fridge for up to five days. Freezes well for longer storage.