-Preheat the oven to 350°F. Butter two 9-inch cake pans. Line the bottoms with parchment rounds and butter the parchment. In a bowl, combine the almond meal, baking soda, and cinnamon. In a large bowl, whisk together the egg yolks, 1⁄3 cup 
of the sugar, the lemon zest,
 and lemon juice until smooth.

-Beat the egg whites on medium speed until frothy, about 2 minutes. Add the salt and cream of tartar and beat on medium-high speed until soft peaks form, about 2 minutes. Gradually add remaining 1/3 cup sugar, 1 tablespoon at a time, beating until stiff peaks form.

-Add the almond mixture to the egg yolk mixture, stirring with a spoon. Fold in one-third of the beaten egg whites to lighten the batter. Then, in 2 additions, gently fold in the remaining whites until just incorporated. Spoon the batter into the prepared pans, dividing it evenly.

-Bake the cakes until brown and a toothpick inserted into the center comes out clean, about 25 minutes. Let cool completely in the pans. Then transfer the cakes to wire racks.

-To make the lemon curd, set a fine-mesh sieve over a bowl. In
 a heavy saucepan over medium-high heat, combine the butter, granulated sugar, lemon juice, and lemon zest, stirring, until the sugar dissolves and the mixture just comes to a simmer. In another bowl, whisk together the eggs and egg yolk. Slowly add the hot lemon mixture to the eggs, whisking constantly. Pour the lemon-egg mixture back into the same saucepan and cook over medium-low heat, stirring constantly, until the curd thickens (do not boil), about 2 minutes. Immediately pour the curd into the sieve, pushing the curd through with a rubber spatula. Let cool slightly in the bowl. Cover with plastic wrap, pressing it directly onto the surface of the curd to prevent a skin from forming. Refrigerate until chilled, at least 6 hours. Just before you are ready to frost the cake, transfer 2⁄3 cup of the cold curd to a bowl and set aside to spread on each cake layer before frosting.

-To make the Whipped Lemon Frosting, beat the cream and powdered sugar in a bowl until soft peaks form. Fold one-third of the whipped cream into the remaining lemon curd to lighten it, and then fold in the remaining whipped cream just until incorporated. Makes about 2 cups (16 fl oz/500 ml).

-To assemble the lemon almond cake, put 1 cake layer on a cake stand. Using a rubber spatula, evenly spread half of the reserved lemon curd on top of the cake. Spread about one-quarter of the frosting over the curd. Top with the second cake layer. Evenly spread the top of the cake with the remaining curd, then spread the remaining frosting over the top. Place a few toothpicks in the top of the cake, and cover with plastic wrap. Refrigerate until ready to serve.