This is the classic German mandeltorte—a not-too-sweet almond cake with just a hint of citrus. The extra egg white makes a lighter cake. Pecans may be substituted for the almonds. Please read About Tortes.
Have all ingredients at room temperature, about 70°F. Preheat the oven to 325°F. Grease and flour the bottom(s) of two 8 × 2-inch round cake pans or one 8-inch springform pan and line the bottom(s) with rounds of parchment paper.
Grind to a fine meal in a food processor or coffee/spice grinder:
Beat in a large bowl, or in a stand mixer with the whisk attachment, on high speed until thick and pale yellow, about 2 minutes:
Fold in the almonds, along with:
Using clean beaters, beat in another large bowl on medium speed until soft peaks form:
Gradually add, beating on high speed:
Beat until the peaks are stiff but not dry. Use a silicone spatula to fold one-quarter of the egg whites into the almond mixture, then fold in the remaining whites. Scrape the batter into the pan(s) and spread evenly. Bake until a toothpick inserted into the center comes out clean, about 20 minutes in round pans, 50 to 55 minutes in a springform pan.
Let cool completely in the pan(s) on a rack; the center will sink as it cools. To level and remove from the pan, see About Tortes.
Frost (and fill, if baked in layers) with:
Or leave unfrosted and fill layers with:
and sprinkle with: