Restaurants serve it with a scoop of vanilla gelato, pastry shops serve it in a variety of ways. The richest way I found was with a layer of ganache on top, then a sprinkling of the requisite powdered sugar. This is one is by far the easiest to make, and it's also gluten-free.
(makes one 9-inch cake)
9 ounces (255 g) good quality dark chocolate, chopped into small pieces
1 cup (225 g) butter
¼ cup (25 g) cocoa powder
1 tablespoon almond extract
1 ¼ cup (250 g) granulated sugar
1 ½ cups ground blanched and toasted almonds
6 eggs, room temperature
Preheat an oven to 310°F and line the bottom of a 9-inch spring form pan with parchment paper.
Slowly melt the chocolate and butter over a double-boiler. In a stand mixer with a whisk attachment, whisk together the melted chocolate mixture, the cocoa powder, almond extract and sugar until combined. Add the ground almonds and whisk until combined. Add the eggs one at a time, adding each egg after the first has been incorporated into the mixture. Pour the mixture into the spring form pan. Make sure the mixture is level and smooth on top. Bake for 50-60 minutes. Cool and serve with chocolate spirals or shavings and powdered sugar. Serve with gelato or whipped cream. Buon Appetito!