Smoked salmon frittata

• 1/2 package of frozen spinach (about 250 g)
• 1 medium onion chopped
• 1 tbsp olive oil
  
• 3 eggs
• 1/2 c. mozzarella
• 3 oz. smoked salmon
• S+P

Heat spinach with onion with oil for about 5 min until onions get tender.
Mix all the remaining ingredients.
Pour into a baking pan and bake for 20-25 min at 375F.