Preheat your oven to 350°F and grease a 9-inch cake pan.
In a double boiler or microwave-safe bowl, melt the chocolate and butter together, stirring until smooth.
In a mixing bowl, whisk together the sugar, eggs, and salt until well combined.
Add the melted chocolate mixture to the egg mixture and whisk until well combined.
Pour the batter into the prepared cake pan and smooth the top with a spatula.
Bake the cake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes, then carefully remove it from the pan and let it cool completely on a wire rack.
Once the cake has cooled, you can top it with whipped cream or fresh berries, or dust it with cocoa powder or powdered sugar.