In a large bowl whisk together the milk, 1/3 cup olive oil, eggs and salt.
In another bowl mix the flour and baking powder together, and stir into the wet ingredients.
Thoroughly squeeze all the moisture from the spinach and set aside.
Saute the onion in a non-stick fry pan with 1 tsp. olive oil until translucent. Add the onion to the spinach and mix well.
Add the spinach/onion mixture, ham and cheese to the dough and mix well. Pour into the prepared dish. Bake for 1 hour or until a tester comes out clean.
Nutrition calculation is an estimation only. If you need nutritional calculations for medical reasons, please use a source that you trust.