Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans by greasing them with butter or non-stick spray then dusting with flour.

In a large bowl, whisk together the all-purpose flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt until smooth.

In another bowl, mix the vegetable oil, buttermilk, hot water, eggs, and vanilla extract until smooth and combined.

Gradually pour the wet mixture into the dry ingredients, folding gently until just combined.

Divide the batter evenly between the prepared cake pans and bake for 30-35 minutes.

Cool the cakes in the pans for about 10 minutes before transferring to a wire rack to cool completely.

Combine egg whites and dark brown sugar in a heatproof saucepan; whisk over medium heat until the sugar dissolves.

Transfer the mixture to a stand mixer and beat on high speed until stiff peaks form, about 5-7 minutes.

Gradually add softened unsalted butter and dulce de leche, mixing until smooth.

Frost the top of the first cooled cake layer with a generous amount of frosting, then add the second layer on top and frost the entire cake.

For the ganache, heat heavy cream until steaming, then pour over chopped dark chocolate and stir until smooth.

Drizzle ganache over the frosted cake and allow it to set before slicing and serving.