Tiramisu Yule Log

Heat oven to 350°F with rack in middle. Butter pan and line bottom and sides with 1 sheet of parchment paper. Butter paper and dust with additional flour, knocking out excess.

Beat together yolks, vanilla, and 1/2 cup sugar in a large bowl with an electric mixer at high speed until thick and pale and mixture forms a ribbon that takes 2 seconds to dissolve when beaters are lifted, 5 to 8 minutes in a stand mixer or 8 to 12 minutes with a handheld. Sift half of flour over yolks and fold it in gently but thoroughly, then sift and fold in remaining flour.

Beat whites with salt and cream of tartar in a large metal bowl with cleaned beaters at medium speed until they just hold soft peaks. Beat in remaining 2 tablespoons sugar, 1/2 tablespoon at a time, and continue to beat until whites just hold stiff peaks.