Heat oil in sauté pan over medium heat. Add onions, then cook and stir 3-4 minutes until soft and slightly golden. Add tomatoes and spinach, then cook 1-2 minutes or until spinach is wilted.
Whisk eggs in medium bowl, then add yogurt and whisk until smooth. Add spinach mixture and cheese and stir to blend.
Pour mixture into 9-inch pie plate. Bake 30-35 minutes or until set.
Pour mixture into 9-inch pie plate. Bake 30-35 minutes or until set.
