Mocha Cake with Swiss Meringue Buttercream

Ingredients

• 3/4 cup cocoa powder sifted, plus more for dusting
• 2 1/4 cups flour
• 3/4 teaspoon baking powder
• 1 teaspoon baking soda
• 3 eggs
• 3/4 cup butter
• 1 3/4 cups sugar
• 1 1/2 teaspoons vanilla
• 3/4 cup buttermilk
• 1 cup hot coffee strong, freshly brewed
• 1 teaspoon fine sea salt
• 6 large egg whites
• 2 cups granulated sugar
• 2 cups unsalted butter room temperature, cubed
• 1/4 teaspoon kosher salt
• 1 teaspoon vanilla
• 1 1/2 tablespoons espresso powder
• 5 ounces bittersweet chocolate chopped, melted and cooled