1. Preheat oven to 350 degrees. Butter a 9-inch springform pan. Line with a parchment round; butter parchment. Spread almonds in a single layer on a baking sheet. Bake, stirring occasionally, until fragrant and golden brown, about 15 minutes. Let cool completely. Meanwhile, in a heatproof bowl set over (not in) a pan of simmering water, melt butter and chocolate together. Let cool.

2. In a food processor, pulse almonds until finely ground. Add flour, salt, and cinnamon, and pulse until combined.

3. In a mixer fitted with the whisk attachment, whisk eggs and brown sugar on high until thick and pale, about 6 minutes. Fold in chocolate mixture, then flour mixture. Transfer batter to prepared pan. Bake, rotating pan halfway through, until cake is puffed and a tester inserted in center comes out clean, about 25 minutes.

4. Let cool 10 minutes on a wire rack. Release sides of pan and remove cake; let cool completely on rack. If desired, dust with confectioners' sugar and serve with ice cream. (Torte can be stored at room temperature, covered, up to 1 day.)