Preheat oven to 400 degrees. Beat 8 eggs in a medium bowl and add in 1/4 cup milk, salt and pepper. Set aside.
Over medium heat in a cast-iron pan or oven-proof skillet, saute bacon until fat renders. Add in onions and cook until they begin to caramelize, stirring occasionally. Add in the tomatoes and kale or chard, cook for about 30 seconds, and pour the egg mixture over the other ingredients. Sprinkle the mozzarella on top. Cook for 30 seconds on the stove.
Put the pan into the pre-heated oven and bake for about 10 minutes, til the edges begin to brown and pull slightly away from the pan. Add additional salt and pepper to taste.