Legend says this cake exists because a baker on Capri forgot the flour entirely, realized partway through that there was no fixing it, and served the cake anyway. Whether that's true, or a story invented well after the fact to make a good cake sound even better, the result is the same either way: dense, intensely chocolatey, with a crackled top that no amount of flour could ever have improved on.
Serves 8–10.
Melt the chocolate and butter together gently, either over a double boiler or in short bursts in the microwave, stirring until smooth. Let it cool slightly.
Whisk the egg yolks with half the sugar until pale and thick. Stir in the melted chocolate mixture, the almond flour, and the liqueur if using.
In a separate, clean bowl, whip the egg whites with the salt until foamy, then gradually add the remaining sugar, continuing to whip until you reach soft, glossy peaks.
Fold a third of the whipped whites into the chocolate mixture to loosen it, then gently fold in the rest in two more additions, taking care not to deflate them -- this is what gives the cake its lift, since there's no flour here to do any of that work for you.
Pour into a buttered and lined springform pan, and bake at 180°C (350°F) for thirty-five to forty minutes, until the top has cracked and a skewer inserted in the center comes out with a few moist crumbs still clinging to it, not wet batter. Cool completely in the pan before removing -- this cake is fragile while it's still warm. Dust with powdered sugar before serving.
If the cake sinks dramatically in the center as it cools, the egg whites were deflated during folding, either overmixed to begin with or handled too roughly once they went into the batter. If it comes out dense and heavy rather than properly rich, the whites weren't whipped to real soft peaks before folding, or too much of that air was knocked back out along the way. And if the texture turns out dry rather than fudgy, it was overbaked; pull it as soon as a skewer comes out with moist crumbs, since this cake, unlike most others, should never come out of the oven fully clean.
A woman celebrating her hundredth birthday filled nearly a third of the dining room with four generations of her own family, crowded around tables pushed together for the occasion. When Chiara carried out a torta caprese with a single candle -- a hundred seemed, reasonably, like a fire hazard -- the entire restaurant stood up and sang, completely unprompted, strangers at other tables included.
She told my father afterward, quietly, that she couldn't really taste much of anything anymore at her age, but had wanted the cake anyway, entirely for the singing. He says it's the only time in years he's seen the whole dining room cry and laugh in the same minute.