Chef Tess' Favorite Chocolate Layer Cake
2 ½ cups (12 1/2 ounces) all-purpose flour
2 teaspoons baking soda
1 teaspoon baking powder
½ teaspoon salt
¾ cup hot water
½ cup (1 1/2 ounces) Dutch-processed cocoa powder
2 teaspoons vanilla extract
1 cup butter, cut into 16 pieces and softened
2 cups (14 ounces) granulated sugar
2 large eggs
1 cup buttermilk, room temperature
Easy Buttercream Frosting
1 ¼ cup unsalted butter, softened
3 cups confectioners' sugar (5 ounces)
Pinch table salt
2 tsp. vanilla extract
2 Tbsp heavy cream
1. FOR THE CAKE: Adjust oven rack to middle position and heat oven to 350 degrees. Grease 2 (8-inch) round cake pans with baking spray with flour. Whisk flour, baking soda, baking powder, and salt together in a bowl; set aside. In the second bowl, whisk hot water, cocoa, and vanilla until smooth; set aside.
2. Using a stand mixer fitted with a paddle, beat butter and sugar on medium-high speed until light and fluffy, about 3 minutes. Add eggs, one at a time, and mix until incorporated. Reduce speed to low and add flour mixture in 3 additions, alternating with buttermilk in 2 additions, until combined. Slowly add cocoa mixture until incorporated.
3. Divide batter evenly between prepared pans. Bake until a toothpick inserted in center comes out with few crumbs attached, about 30 minutes. Let cakes cool completely in pans, about 1 hour. (Cooled cakes can be wrapped in plastic wrap and stored at room temperature for up to 2 days.)
4. FOR THE FROSTING: In a standing mixer fitted with whisk attachment, beat butter at medium-high speed until smooth, about 20 seconds. Add confectioners' sugar and salt; beat at medium-low speed until most of the sugar is moistened, about 45 seconds. Scrape down bowl and beat at medium speed until the mixture is fully combined, about 15 seconds; scrape bowl, add vanilla, and heavy cream, and beat at medium speed until incorporated, about 10 seconds, then increase speed to medium-high and beat until light and fluffy, about 4 minutes, scraping down bowl once or twice.