Preheat oven to 375 degrees. Grease the bottom of a 9 inch pie plate.
Beat eggs with Greek yogurt until yolks are broken and the mixture is fluffy and well combined.
Add in bread cubes, onion, spinach, tomato, salt, pepper, cayenne pepper, onion powder and half of the feta cheese crumbles. Stir until all vegetables and bread are well coated with egg mixture.
Pour mixture into pie plate. Make sure all spinach leaves are within the egg mixture as they will burn if sticking out. Top with remaining feta cheese and shredded mozzarella.
Bake for 45-50 minutes, until a toothpick inserted into the center comes out clean. Serve warm and enjoy!
