Step 1

In a food processor, combine the flour and salt. Cut the vegan butter into small chunks and add to the bowl. Pulse a few times to lightly mix the ingredients. Add the water and apple cider vinegar and pulse a few more times to form a crumbly dough. (You can also combine all the ingredients in a large bowl, except the water and massage with your hands to form a crumbly dough. Add the water and massage to form a shaggy dough.) Do not over-knead the dough (see Notes).

Step 2

Transfer the dough to a work surface and bring together to form a ball. Cover with reusable wrap and chill in the refrigerator for 1 hour.

Step 3

Preheat the oven to 425°F (220°C).

Step 4

Lightly sprinkle the work surface with flour. Using a rolling pin, roll out the dough into a 12-inch circle. If needed, lightly sprinkle the dough with flour to stop the rolling pin from sticking.

Step 5

Roll the dough around the rolling pin. Gently lift the dough and unroll over an 11-inch tart pan with removable bottom. Press into the bottom and up the sides of the pan. For a clean edge, trim excess dough with a knife. Patch any cracks with excess dough. Poke a few holes in the base with a fork. (This will stop the base from lifting as it cooks. There’s no need to use pie weights with this crust.) Transfer the tart pan to a baking sheet and blind-bake for 15 minutes. Remove from the oven and let cool. Reduce the oven temperature to 350°F (180°C).

Step 6

Heat the coconut oil in a large skillet over medium heat. Add the garlic and onion and cook, stirring frequently, until the onion is softened, about 10 minutes. Add the mushrooms and cook until the juices they release have evaporated and the mushrooms have softened and browned, about 10 minutes. Add the spinach, cover with a lid, and let the spinach wilt, 2 to 3 minutes. Remove from the heat.

Step 7

In a food processor or high-speed blender, combine the silken tofu, almond milk, nutritional yeast, arrowroot powder, turmeric, onion powder, garlic powder, sea salt, black salt, and pepper. Pulse until smooth.

Step 8

Pour the tofu mixture into the skillet and mix together with the cooked vegetables to combine. Pour the filling into the pre-baked crust in a smooth and even layer. Bake until the filling is golden and firm, about 40 minutes. Let cool slightly before slicing.