This gluten-free chocolate dump cake hits all the notes you want in a gluten-free cake - soft, fudgy crumb, dense chocolate flavor, and creamy, dreamy frosting.
Preheat the oven to 375℉ and place a baking sheet on the lowest rack to catch any drips as the cake bakes on the middle rack. Grease a tube pan.
In a small bowl, stir together the 1 cup whole milk and 1 teaspoon apple cider vinegar.
In a 2- to 3-quart pot, mix together the 2 cups granulated sugar, 4 ounces unsweetened chocolate, ½ cup unsalted butter, and 1 cup of water. Place over medium heat and stir occasionally until all of the ingredients are melted and blended. Remove from the heat and let cool slightly.
Meanwhile, sift together the 1 ¾ cups oat flour, ½ cup almond flour , 2 teaspoons baking soda, 1 teaspoon baking powder, and 1 teaspoon fine sea salt.
When the chocolate in the pot has cooled a bit, whisk in the milk mixture and 2 large eggs. In several additions, whisk in the dry ingredients. When the mixture is smooth, add the 1 teaspoon pure vanilla extractand whisk once or twice to blend.
Pour the batter into the tube pan and bake on the middle rack until a skewer inserted in the center comes out clean, about 30 to 35 minutes. Let the cake cool for 10 minutes, then remove from the pan and cool on a rack, then let cool completely.
Meanwhile, melt the 3 ounces semisweet chocolate chips and ½ cup unsalted butter in a double boiler, then let cool to room temperature. Ice the top of the cooled cake.
Notes
Let the melted chocolate mix cool. Important! After you melt the chocolate, sugar, water, and butter together, let the mixture cool a bit before adding the eggs. This will prevent any possible scrambling of the eggs if the chocolate is too hot.
Bake on a baking sheet. Place a baking sheet underneath the tube pan to catch any potential drips during baking.
Grease the pan very well. My tube pan is a non-stick pan, but I still butter it very well and dust it with a little oat flour or cocoa powder to help it slip out of the pan easily.
Cool completely. Let the cake cool in the pan for at least 10 minutes before carefully removing it to a rack to cool completely. By "completely," I mean that it will be at room temperature, and not warm.
The cake will be tender. This is a soft, moist cake. Treat it gently when removing it from the bundt pan to prevent it from breaking.
Make it dairy-free. Swap non-dairy butter and milk for the butter and milk.