Made with dark chocolate and almond flour, this special occasion-worthy cake is surprisingly light and airy thanks to the addition of egg whites and just happens to be gluten-free. Serve with whipped creme fraiche and a tumble of fresh raspberries.
Whipped Creme Fraiche: Whisk cream with vanilla and salt until thickened and silky but not yet forming peaks. Add sugar and creme fraiche; whisk to soft peaks, 1 to 2 minutes more. Serve immediately, or cover and refrigerate in an airtight container up to 8 hours; stir before using.
Cake: Preheat oven to 350 degrees. Butter a 9-inch springform pan. In a mixer fitted with the paddle attachment, beat butter with 3/4 cup granulated sugar on medium-high speed until pale and fluffy, 2 to 3 minutes. Beat in egg yolks, one at a time. Beat in chocolate and vanilla. Add almond flour and salt; beat to combine. In a separate bowl fitted with the whisk attachment, beat egg whites on low until frothy. Increase speed to medium-high and beat to soft peaks, about 1 minute. Gradually add remaining 1/4 cup granulated sugar, beating until stiff but not dry peaks form, about 1 minute more. Stir one-third of egg-white mixture into batter until no streaks remain. Gently fold in remaining egg-white mixture just to combine (do not overmix). Transfer to prepared pan; gently smooth top with an offset spatula.
Bake until puffed slightly and set along edges but still slightly wobbly in center, 30 to 35 minutes. Transfer to a wire rack; let cool completely, about 2 hours. Remove sides of pan. Using a spatula, gently lift cake from pan; slide onto a cake plate. Lightly dust with confectioners' sugar. Cut into wedges; serve with creme fraiche and raspberries.