In a bowl, mix all the ingredients for the pie crust: water, flour, oil, and salt. Mix with a fork until the flour absorbs all the water.
Transfer onto a worktop and knead with your hands for 5 minutes, or until the dough is smooth and elastic. You can do this in a kitchen aid if you prefer.Shape it into a ball, cover it with a kitchen cloth and let it rest for 30 minutes, at room temperature.
Make the zucchini pie filling
Thinly slice the red onion, then fry it for 3 minutes in a non-stick pan with the olive oil. Once the onion is soft, add the sliced zucchini, a dash of tap water, season with salt and pepper, and cook for 5 to 10 minute, or until the zucchini is soft (but not mushy, so don't overcook it).While the zucchini cooks, you can prep the chickpea flour mix.
Make the chickpea batter
In a bowl, add chickpeaflour, water, oliveoil, nutritionalyeast, a pinchofsalt, and pepper. Blend with an immersion blender for about three minutes. You can also use a regular blender.The batter needs to be completely smooth. Now, set aside, and go back to the dough.
Roll the dough
First, preheat the oven to 390F or 200C.With a rolling pin, roll the dough ball. Dust the worktop and the rolling pin with flour, to prevent the dough from sticking.Make the rolled dough as large as your pie dish, so that it can cover the bottom and sides.
Oil your pie dish or line it with parchment paper if you prefer. Transfer the dough into the pie dish, making sure the dough cover all sides, up to the rim.
Now add the baking powder to the chickpea batter, and whisk till dissolved. You can also blitz it up with the blender.Add the zucchini to the chickpea batter and mix them with a spoon. The zucchini should be well distributed in the batter.
Transfer the chickpea-zucchini mix into the pie crust. Move the zucchini around with a spoon to make sure they are evenly distributed.Fold the excess pie crust onto the filling, to create a rim. If you want, you can sprinkle with dairy-free cheese/parmesan.Bake for 30 minutes at 390F or 200C.
Your zucchini pie is ready when is crisp and golden on top, but stil moist and soft inside.