Preheat the oven to 200C/400F degrees.
Grease and line the bottom of an 8 inch spring form cake tin with parchment paper.
Heat the olive oil in a frying pan on a medium heat and cook the grated zucchini and spring onions for 10-12 minutes, stirring occasionally until it is slightly golden.
Whisk the egg whites until they form stiff peaks.
In another bowl, add the zucchini, Feta cheese, Parmesan cheese, egg yolks and seasonings. Mix thoroughly.
Add the coconut flour and baking powder and mix until combined.
Gently fold in the whisked egg whites.
Pour the mixture into the cake tin and bake for 40 minutes.