Preheat oven to 180 °C (350 °F). Grease an 8–9‑inch springform pan, line the bottom with parchment paper, and dust the inside with cocoa powder.

Melt butter and dark chocolate together (double boiler or microwave), stirring until smooth. Allow to cool slightly.

In a bowl mix the chocolate‑butter with vanilla extract, salt, and sifted cocoa powder until blended.

In a separate bowl, whisk the yolks with half the sugar until pale and creamy.

In a clean bowl, beat the egg whites, gradually adding the remaining sugar, until medium‑stiff peaks form.

Fold one‑third of the egg whites into the chocolate yolk mixture to lighten it, then gently fold in remaining whites just until no streaks remain. Be careful not to deflate the batter.

Fold in the almond flour until fully incorporated.

Pour batter into prepared pan, tap gently to settle. Bake for 25–30 minutes, until a skewer inserted in the center comes out with moist crumbs or faint batter. The top will form a thin crust.

Cool for about 30 minutes in the pan before releasing and cooling to room temperature. Chill in fridge for firmer texture if desired.

Dust with powdered sugar or cocoa before serving. Optionally serve with whipped cream or fresh berries.