Make the genoise: Preheat oven to 400 degrees, with rack in lower third. Butter two 9-inch round cake pans. Line with parchment; butter the parchment. Dust with cocoa powder, tapping out excess.
Whisk together flower, salt, and cocoa powder in a bowl.
Put eggs, egg yolks, and granulated sugar in the heatproof bowl of an electric mixer. Set over (not touching) a pan of simmering water, and whisk until sugar has dissolved and mixture is warm to the touch. Attach bowl to mixer fitted with whisk attachment. Beat on medium-high speed for 2 minutes. Raise speed to high. Beat until mixture is pale and thick, about 4 minutes more.
Remove bowl from mixer. Sift flour mixture over the top; using large rubber spatula, carefully fold into egg mixture, cutting through middle and lifting gently over sides. When almost incorporated, pour melted butter down side of bowl; gently fold in to incorporate.
Divide batter evenly between prepared pans. Bake until centers spring back when lightly touched, about 15 minutes.
Let cool in pans on a wire rack for 15 minutes. Run a knife around sides of pan. Invert onto rack; remove parchment, and turn right side up on rack.
Make the Kirsch simple syrup: Heat sugar and water in a small saucepan over medium-high heat, stirring frequently, until sugar has dissolved. Bring to a boil. Remove from heat and stir in kirsch. (The syrup can be refrigerated in an airtight container for up to 1 month).
Make the cherry filling: Whisk reserved cherry juice, sugar, kirsch, and cornstarch in a small saucepan until smooth. Cook over medium heat, stirring constantly, until mixture is thick enough to coat the back of a spoon, about 8 minutes. Let cool slightly. Combine syrup and cherries in a medium bowl. Cover and refrigerate until ready to use, up to 2 days.
Make the ganache: Bring cream to a boil in a small saucepan over medium heat. Pour over chocolate in a bowl. Let stand 5 minutes. Slowly whisk until smooth. Let cool completely, stirring often with a rubber spatula.
Make the espresso whipped cream: Beat cream until soft peaks form. Add sugar and espresso powder, and beat until soft peaks return.
Assemble the cake: Slice each cake in half horizontally. Place once cake layer, cut side up, on a cake stand. Brush top with 1/4 cup kirsch syrup. Spread with 2 cups whipped cream, leaving a 1/2 inch border. Remove cherries from filling syrup with slotted spoon, and transfer to medium bowl. Scatter 1 1/4 cup cherries evenly over whipped cream. Drizzle with 2 tablespoons filling syrup. Repeat 2 times . Place final cake layer, cut side down, on top, and spread with ganache. Serve immediately.