Preheat your oven to 350°F (175°C).
Grease and line a 9-inch round cake pan with parchment paper.
In a large bowl, whisk together the flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt.
In another bowl, mix the dairy-free yogurt, buttermilk, melted coconut oil, and vanilla extract until smooth.
Add the wet ingredients to the dry ingredients, mixing until just combined.
Gradually add the hot water, mixing until the batter is smooth.
Pour the batter into the prepared pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.