Coat bottom of skillet with oil. Add onion and, stirring frequently, cook until softened, 3-4 minutes.
about 2 tbsp extra virgin olive oil
In a medium bowl, whisk together eggs, oregano, salt, and pepper.
½ tsp oregano
½ tsp salt
¼ tsp black pepper
Preheat oven to broil and position rack about 4 inches from the top.
Add garlic and tomatoes to skillet. Stir to combine and cook for 1-2 minutes.
Add spinach and stir to combine.
Spread out ingredients evenly in the skillet. Pour in egg mixture. As eggs set around the edge of the skillet, gently lift cooked portions with a spatula to allow uncooked egg to flow underneath. Cook until bottom and sides are firm but the top is still runny, 6-8 minutes.
Sprinkle feta over top. Place skillet in the oven under the broiler until the top is set, 2-3 minutes.
1 (4 oz) pkg crumbled feta cheese
To serve, cut frittata into wedges and place on a plate. Enjoy!