Preheat the oven to 350°F. Butter a 9-inch round cake pan.

To make the flourless chocolate cake, fill a small saucepan with 1 inch of water and set over medium heat. Place the butter, chocolate and espresso powder in a heatproof bowl and set on top of the simmering water to melt slowly. When the chocolate is almost melted, remove the bowl from heat and stir until mixture is smooth. Transfer the melted chocolate mixture to a large mixing bowl and allow to cool for 5 minutes.

Add the egg yolks, almond flour and vanilla extract to the cooled chocolate mixture and whisk well to combine.

To make the meringue, whip the egg whites with ½ teaspoon kosher salt in a stand mixer on medium-low speed. When the egg whites are frothy, slowly add the sugar to the bowl.

Increase mixer speed to medium and whisk until the meringue is thick and glossy with stiff peaks, about 5 minutes.

Add ¾ of the glossy meringue to the bowl with the chocolate mixture. Use a rubber spatula to gently fold the meringue into the chocolate until lightened in color and there are no streaks of chocolate left.

Add the remaining reserved meringue to the bowl, and fold it in, until it marbles throughout, leaving a few streaks of chocolate and meringue.

Carefully pour the cake batter into the prepared cake pan in an even layer, gently smoothing the top with an offset spatula. Bake the cake for 1 hour until puffy and crispy on top. As the cake cools, it will collapse slightly in the center.

To make the amaretto-soaked berries, combine the berries, amaretto, vanilla extract, sugar and lemon juice in a medium bowl. Stir to coat the berries with the sugar and liqueur. Serve with the cooled cake.