Preheat the oven to 300 degrees F (150 degrees C).

Combine chopped chocolate and hot coffee in a bowl. Stir occasionally until chocolate is melted and mixture is smooth. Set aside.

Sift sugar, flour, cocoa powder, baking soda, baking powder, and salt together in a large bowl.

Beat eggs in a bowl using an electric mixer until slightly thickened and lemon-colored. Slowly add oil, buttermilk, vanilla extract, and melted chocolate mixture. Beat until well combined. Add sugar-flour mixture; beat on medium speed until just combined. Divide batter between the prepared cake pans.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 1 hour to 1 hour and 10 minutes. Let cool completely in pans on wire racks, about 30 minutes. Invert layers onto racks.

While cakes are cooling, bring heavy cream, sugar, and corn syrup to a boil over low heat in a small saucepan. Whisk until sugar dissolves. Add chocolate; whisk until melted. Add butter; whisk until smooth. Let ganache frosting cool until spreadable, about 10 minutes.

While frosting and cakes continue to cool, puree raspberries in a food processor. Press through a fine mesh strainer with the back of a spoon into a saucepan. Pour in sugar and cornstarch; bring to a boil over medium-low heat. Cook until thickened and reduced, 5 to 7 minutes. Stir in lemon zest. Remove raspberry filling from heat.

Cut each cake layer in 1/2 horizontally to produce 4 equal layers. Spread 1/3 raspberry filling onto each of 3 layers and stack. Place top layer onto cake. Spread ganache frosting evenly from center of top layer down the sides of the cake.