How to Make It
In a large, stainless steel bowl, beat the cream until softly whipped. Cover and refrigerate.
In a medium bowl, beat the egg whites until frothy, about 30 seconds. Beat in 5 tablespoons of the sugar, 2 tablespoons at a time, beating until the whites are firm and glossy. In a small bowl, beat the egg yolks with the remaining 3 tablespoons of sugar until pale yellow and thick. Fold the yolk mixture and the lemon zest into the egg whites until just combined. Fold in the whipped cream. Scrape the mixture into a glass or ceramic bowl, cover with plastic wrap and freeze for about 2 hours, until the semifreddo is firm.
Preheat the oven to 350°. Butter a 9-inch springform pan. Line the bottom with parchment paper and butter the paper; flour the pan, tapping out any excess. In a food processor, pulse the almonds until finely ground. Transfer the almonds to a medium bowl. Working over the bowl, sift the confectioners' sugar with the flour and 1/2 teaspoon of salt. Stir in the orange peel.
In a large bowl, using clean beaters, beat the egg whites with a pinch of salt until stiff peaks form. Sprinkle the almond mixture over the egg whites and fold just until incorporated. Fold in the butter and orange extract. Scrape the batter into the prepared pan and bake for about 35 minutes, until golden brown. Set the pan on a rack and let the cake cool. Unmold the cake and peel off the paper.
Cut the cake into wedges and transfer them to plates. Top with scoops of semifreddo and serve.
Orange sections or berries.