01 - Preheat oven to 350°F. Grease an 8-inch round springform pan and line the base with parchment paper.
02 - In a heatproof bowl placed over simmering water, melt dark chocolate and butter together, stirring until smooth. Remove from heat.
03 - Whisk granulated sugar, sea salt, and vanilla extract into the chocolate mixture until fully incorporated.
04 - Add eggs one at a time, whisking thoroughly after each addition until the batter is glossy and thick.
05 - Pour the batter into the prepared pan and smooth the top evenly.
06 - Bake for 25 to 30 minutes, until edges are set but the center remains slightly wobbly.
07 - Cool completely in the pan on a wire rack for approximately 1 hour; the center will sink slightly.
08 - Remove cake from the pan and transfer to a serving plate. Arrange fresh raspberries on top.
09 - Dust with powdered sugar before serving if desired.