In a large sauté pan, fry the bacon over medium until crispy on both sides. Set aside to drain on paper towels, leaving bacon grease in the pan.

Add the onion to the pan with the bacon grease and sauté over medium heat for about 10 minutes, until translucent and starting to brown. Set aside to cool slightly.

Preheat oven to 350 degrees F and grease a 9X13 inch pie pan.

In a large bowl, whisk together eggs, cream, salt, cayenne, and chives. Stir in 3/4 cup of Swiss and gruyere cheeses.

Pour the egg mixture into the prepared pie pan. Sprinkle with the cooked onion. Cut the bacon into small pieces and sprinkle over the eggs. Push the onion and bacon into the eggs. Sprinkle with remaining 1/4 cup of each cheese.

Bake for 30-40 minutes, until knife is inserted in the center and comes out clean.

Serve warm!