Preheat the oven to 350°F (180°C). Lightly grease a 9-inch x 9-inch square cake pan with oil. Glass or ceramic pans work the best.
Directly in the cake pan (no bowl is needed for this recipe), add the flour, sugar, unsweetened cocoa powder, salt, and baking soda. Whisk to combine.
Make 2 wells in the dry ingredients and add the vinegar in one of the wells and the oil in the other well.
Pour the water, at room temperature, over the ingredients and whisk to form a batter with no lump. Careful, don't use boiling water, or the cake will be very chewy. Very cold water may create lumps, especially with gluten-free all-purpose flour.
Bake for 25-30 minutes or until a pick inserted in the center of the cake comes out clean.
Cool the cake down to room temperature before frosting. If you used a glass/ceramic pan, cool the cake in the pan, no need to unmold it. Otherwise, unmold after 10 minutes and cool down on a rack.
Meanwhile, prepare the chocolate ganache
Combine the melted chocolate with coconut cream
Heat the coconut milk or cream in a small pan (you can also use your microwave), then pour over the dark chocolate chips and stir until the chocolate in the ganache is smooth and shiny.
Spread all over the cake before serving
Flour options: you can replace white flour with the same amount of spelt flour or all-purpose gluten-free flour, or oat flour. Oat flour makes the cake very dense and doesn't work in combination with sugar-free sweetener. The texture will be fragile if so. Sugar options: coconut sugar, unrefined cane sugar, or sugar-free option: replace sugar with erythritol or xylitol. Nutrition will be Calories: 176 kcal, Carbs: 17.8g, Sugar: 3.1g, Protein: 2.7 g Fiber: 1.8 g, Net carbs: 16g