large egg yolks
finely grated lemon zest plus 1/2 cup lemon juice
- Set a fine-mesh sieve over a medium bowl. In a heatproof medium bowl, whisk together the egg yolks, lemon zest and juice, salt, and 1 cup of the sugar. Set the bowl over (not in) a saucepan of simmering water and cook, stirring constantly, until the lemon mixture becomes opaque and has thickened slightly, 12 to 15 minutes.
- Pour the lemon mixture through the sieve into the bowl. Place a piece of plastic wrap directly on the surface of the lemon mixture and refrigerate until completely cool, at least 2 hours.
- Using an electric mixer, whip the cream and the remaining ½ cup of sugar on medium until soft peaks form, 2 to 3 minutes. In 3 additions, gently fold the whipped cream into the lemon mixture. Pour into an 8-by-4-inch loaf pan or another 6-cup pan, cover, and freeze until firm, at least 4 hours.
- Meanwhile, heat oven to 375° F. Spread the almonds on a rimmed baking sheet and toast, tossing once, until golden brown, 4 to 6 minutes. Serve the semifreddo sprinkled with the almonds.