Preheat the oven to 375 F. Spray a 9 inch glass pie plate with nonstick spray. Heat the oil in a large nonstick skillet over medium-high heat. Add the onion and cook, stirring occasionally, until tender, about 5 minutes. Add the spinach and cook, stirring, until the spinach is wilted and any liquid is evaporated, 2-3 minutes. Whisk the eggs and egg whites in a large bowl until lightly beaten. Whisk in the milk, ricotta, salt, cayenne, dill, and nutmeg until blended. Stir in the spinach mixture, cheese, and bacon until well combined. Pour into the prepared pie plate. Bake until the top is golden and a knife inserted into the center comes out clean, 35-40 minutes. Let stand 10 minutes before slicing.