Prep the pans: Heat oven to 350°F (175°C). Grease two 8-inch round cake pans and line the bottoms with parchment. Lightly dust with gluten free flour or cocoa and tap out excess.

Whisk the dry mix: In a large bowl, whisk 1¾ cups gluten free all-purpose flour, ¼ cup cornstarch, ¾ cup unsweetened cocoa powder, 1½ teaspoons baking powder, 1 teaspoon baking soda, and ½ teaspoon fine sea salt until well combined.

Combine the sugars and wet ingredients: In another bowl, whisk 1 cup granulated sugar, ½ cup packed light brown sugar, 2 large eggs, and 1 teaspoon vanilla until glossy. Whisk in ½ cup neutral oil.

Add the dairy: Stir in 1 cup buttermilk until smooth. The mixture will look creamy and slightly thick.

Bring in the dry ingredients: Add the dry mix to the wet bowl and whisk gently until just combined. Do not overmix; a few small lumps are fine.

Bloom with heat: Pour in ¾ cup hot coffee (or hot water). Whisk slowly until the batter is smooth and pourable. It will look thin—this is right.

Fill and bake: Divide the batter evenly between pans. Bake 24–28 minutes, or until the centers spring back and a toothpick comes out with a few moist crumbs.

Cool completely: Let cakes cool in pans 10 minutes, then turn out onto racks. Peel off parchment and cool fully before frosting.

Optional frosting (simple chocolate buttercream): Beat ½ cup softened unsalted butter with a pinch of salt until creamy. Sift in 1¾ cups powdered sugar and ¼ cup cocoa; beat until fluffy. Add 1 teaspoon vanilla and 2–4 tablespoons milk or cream until spreadable. For extra punch, melt ¼ cup chocolate and beat in once cool.

Assemble: Place the first layer on a plate, spread frosting, top with the second layer, and finish with more frosting. Keep swirls rustic or go smooth and sleek.