Ingredients

　　1 teaspoon butter

　　1/3 cup chopped yellow onion

　　3 large eggs

　　Salt and ground black pepper to taste

　　2 tablespoons Dijon mustard

　　1 cup cooked fresh or frozen spinach, well drained and squeezed dry

　　2 tablespoons grated Parmesan cheese

　　Combine the butter and onion in a medium nonstick skillet. Stirring constantly, cook over medium heat until the onion has softened, 3 to 4 minutes. In a bowl, beat the eggs with the salt, pepper, and mustard. Add the egg mixture to the skillet and stir briefly to lightly scramble. Without stirring, continue to cook until the eggs are softly set, about 2 minutes. Scatter the spinach over the eggs and sprinkle with the Parmesan cheese. Cover the pan and cook for 1 minute to heat through. Uncover, tilt the pan away from you, and fold half of the omelet over with a spatula to enclose the filling. Cook for an additional 30 seconds before sliding the omelet onto a plate. Cut it in half before serving.

　　Cooks' Note

　　Eggs are an excellent and inexpensive protein source. In addition, the spinach provides significant amounts of the recommended daily allowance of vitamin A, vitamin C, and folate, as well as the minerals calcium and magnesium. If you prefer to use frozen spinach, know that a 10-ounce package will yield 1 cup cooked.

　　Sugar Busters! Quick & Easy Cookbook