Thaw your vegan pie crust for about 10 minutes. Pierce the bottom and the sides of the pie crust so that air pockets don’t form.
Preheat oven to 180°C.
Heat oil in a large skillet. Add onions and mushrooms. Cook over medium heat until mushrooms have release most of their liquid, about 10 minutes. Add spinach and garlic and cook for another 3 minutes. Set aside.
Combine tofu, yeast, cornstarch, lemon juice, turmeric and salt in a food processor or blender and process until smooth and creamy.
Add tofu mixture to sautéed vegetables, stir to combine and spoon mixture into the pie crust.
Using a spatula, spread the mixture around so it’s even on top.
Bake for 30 minutes, or until the top is golden and the center is firm.