Get ready. Preheat your oven to 375°F.
Season the eggs. In a large bowl, whisk together eggs, oregano, dill, pepper, paprika, and baking powder (if using). Season with a pinch of salt.
Mix the remaining ingredients. Add the spinach, onion, parsley, mint, garlic, feta, and milk. Mix well to combine.
Start the frittata. In a 12-inch cast iron skillet (or oven-safe skillet) over medium-high heat, heat enough olive oil to coat (about 2 tablespoons). When it’s shimmering (but before smoking), pour in the egg mixture. Give the skillet a gentle shake to allow the egg mixture to spread well. Cook for about 4 minutes or so, allowing the bottom of the eggs to settle.
Bake the frittata. Transfer the pan to the heated oven until the top is firm and it doesn’t jiggle when you shake the pan, about 8 minutes.
Serve. Remove the frittata from the oven and allow to rest for a few minutes, then slice and serve, with cucumber tomato salad on the side if you’d like. Enjoy!