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