Preheat the oven to 180°C (356°F).

Heat a drizzle of olive oil in a large skillet over medium heat. Add the chopped red onion and minced garlic, sautéing until the onion is soft and translucent.

Add the spinach to the skillet and cook until wilted. If using, add the chopped chili pepper for a bit of heat. Season with salt and pepper to taste. Remove from heat and let cool slightly.

In a mixing bowl, beat the eggs and then whisk in the milk.

Gradually add the flour to the egg mixture, stirring until smooth and well combined.

Add the cooked spinach mixture to the egg and flour mixture, stirring until evenly distributed.

Fold in the crumbled feta and grated mozzarella cheese.

Grease a baking dish with olive oil and pour the mixture into the dish, spreading it out evenly.

Bake in the preheated oven for 20 minutes, or until the top is golden brown and the bake is set.

Garnish with fresh parsley before serving.