HEAT oven to 400°F. COAT 15-1/2 x 10-1/2 x 1-inch jelly-roll pan with cooking spray. LINE bottom with waxed or parchment paper; spray paper.
BEAT egg whites and cream of tartar in mixer bowl with whisk attachment on high speed until foamy. Beating constantly, ADD 1/3 cup of the granulated sugar, 2 Tbsp. at a time, beating after each addition until sugar is dissolved before adding the next. (Rub a bit of mixture between thumb and forefinger; it should feel completely smooth.) Continue beating until whites are glossy and stand in soft peaks.
BEAT egg yolks in clean mixer bowl on high speed until thick and lemon-colored, 3 to 5 minutes. Gradually BEAT IN remaining 1/3 cup granulated sugar until pale yellow and sugar is dissolved. BEAT IN almond extract, vanilla and salt.
MIX almonds and flour in small bowl; sprinkle evenly over egg whites. ADD yolk mixture. FOLD gently but thoroughly until color is uniform and no streaks of white remain. Do not stir. SPREAD in prepared pan.
BAKE in 400°F oven until center springs back when lightly tapped with finger, 10 to 12 minutes.
MEANWHILE MAKE SYRUP: HEAT sugar and water in small saucepan to boiling. REDUCE heat; simmer 1 minute. LET COOL. STIR IN liqueur, if desired.
SPRINKLE clean kitchen towel with powdered sugar. LOOSEN cake from sides of pan with knife. INVERT cake onto towel; carefully peel off waxed paper. TRIM all cake edges with serrated knife. BRUSH syrup evenly on hot cake. ROLL UP cake, starting from short end and rolling towel in with cake. COOL wrapped cake roll, seam-side down on wire rack.
Carefully UNROLL cooled cake; remove towel. SPREAD evenly with about 1 cup frosting; reroll cake. PLACE seam-side down on platter. COVER with about 1 cup frosting, using small spatula to create tree bark effect.
Egg temperature: It’s easiest to separate eggs cleanly when they are refrigerator cold. However egg whites whip up to greater volume when they’ve had a chance to warm up a bit, 20 to 30 minutes. Always begin by separating the eggs. Let the whites stand at room temperature while you prepare the baking pan, equipment and other ingredients.
Add sugar gradually. For optimum volume and smoothest texture, sugar should be added gradually, beginning only after the egg whites or yolks have been beaten to the proper stage. Adding some or all of the sugar before beginning to beat will result in less volume.
What’s a soft peak? The egg white mixture should be beaten until it appears glossy and stands in soft peaks that curl at the tips when the beater is lifted. If the peaks stand straight and tall (stiff peaks), it has been overbeaten.
This recipe is a good source of choline and protein.