Preheat oven to 350°F. Spray 2 (8-inch) tall-sided round cake pans with baking spray with flour.

In a large saucepan, heat beer and butter over medium-low heat until butter is melted. Remove from heat; whisk in sugar and cocoa.

In a large bowl, whisk together flour, baking powder, baking soda, and salt. In a medium bowl, whisk together sour cream, eggs, and vanilla. Whisk sour cream mixture into beer mixture; whisk beer mixture into flour mixture until smooth. Divide batter between prepared pans.

Bake until a wooden pick inserted in center comes out clean, 32 to 36 minutes. Let cool in pans for 10 minutes. Remove from pans, and let cool completely on wire racks. Spread Malted Buttercream between layers and on top and lightly on sides of cake.