Preheat the oven to 350, and line a pie plate with parchment paper.

Caramelize the onions by adding the onions to a hot skillet adding a little water whenever they start to stick. Cook them until they are brown (30 - 35 min) adding water a tablespoon at a time, and then remove them to a bowl.

Place the mushrooms and the spinach in the same skillet, and cook them down until the water is removed. (This will also remove any of the onions that have stuck to the bottom of the skillet).

Stir all of the dry ingredients in a mixing bowl.

Add the onions back into the skillet with the mushrooms and the spinach and stir to combine.

Stir the riced cauliflower into the dry mixture.

Add the water to the dry mixture, and stir just until it is combined.

Quickly, stir the onion mushroom mix into the cauliflower mixture, and spread into the pie plate.

Bake for 30 - 45 minutes or until the top is golden brown.

Remove from the oven and let cool for 15 - 20 minutes before slicing.