Grease 2 pie trays diameter size 6 inch.
Layer with potatoes then chopped onions then capsicums n sprinkle salt.
Mix soy milk with egg whites. Add in sifted flour n baking powder in batches n use a wooden spatula to blend till smooth.
Pour over the two trays.
Bake at 200 c or 400 f for 30 minutes. Cool slightly before serving.
In addition , I also topped with grated mixed cheese at 20 minutes of baking and when done the top is golden brown.
The capsicums offer sweetness to the pie.
I would increase salt or add some fried bacon in the next time to increase the savory taste.