Bring all ingredients to room temperature.
Preheat the oven to 325°F (165°C).
Spray a 9-inch (23 cm) springform pan with baking spray. Line the bottom with parchment paper.
In a small saucepan over low heat, melt the chocolate with the butter, stirring until smooth and silky. Set aside.
In a large bowl, beat the egg whites on medium-low speed. Once they begin to foam, add half the sugar gradually. Increase to medium-high and beat until firm, glossy peaks form. Set aside.
In a separate bowl, beat the egg yolks with the remaining sugar for 4–5 minutes on medium-high speed, until pale, creamy, and the sugar has fully dissolved.
Add the melted chocolate to the beaten yolks and stir to combine.
Add the almond flour, cocoa powder, and instant coffee. Mix until fully incorporated.
Fold in the beaten egg whites in three additions, using gentle circular motions.
Pour the batter into the prepared pan, smooth the top, and bake for 50 minutes.
Turn off the oven and leave the cake inside for 10 more minutes.
Remove from the oven and let rest on a wire rack for 20 minutes before unmolding.
Dust with powdered sugar and transfer to a serving plate.