Preheat the oven to 350 degrees. Grease a 10x15 jelly roll pan and line it with parchment or waxed paper. Grease the paper.

In a large bowl of the electric mixer beat the egg whites until soft peaks form. The soft peak stage is when you lift up the beater and the tip of the peak falls over. Gradually, add 1/3 cup superfine granulated sugar and continue to beat until stiff peaks form (peaks will stand up straight). Set aside.

In a small bowl of the mixer, beat the yolks on high until they are very light and lemony colored. It will take about 6 or 7 minutes. Gradually add the other 1/3 cup superfine sugar while continuing to beat the yolks. Slowly, add the lemon juice and the lemon zest and beat for another minute. Remove the beaters and set the bowl aside.

Take about 1 cup of the egg whites and mix it into the yolks. Gently fold this mixture into the larger egg white bowl. Set aside.

Sift the potato starch and the matzah cake meal two times. Gently add this to the eggs in three additions.

Gently spread the batter on the greased pan and bake in the center of the oven for about 15 minutes or until a clean knife or cake tester comes out clean.

Remove from the oven and let sit for about 5 minutes. Turn the cake out onto a clean dish towel. Roll it up the long way with the towel inside and refrigerate.

To Make Filling:

Combine the sugar and potato starch in a heavy saucepan. Add the cold water. Place on a medium heat. Beat the egg yolks slightly, and add them to the saucepan. Add the lemon zest and lemon juice. With a wire whisk, stir the mixture constantly as it heats. If it is too thick, add more hot water, one tablespoon at a time. As soon as it comes to a boil, whisk more vigorously but for only one minute. Remove from the heat and add the margarine, stirring constantly. Set aside to cool.

To Make Meringue:

n a small saucepan combine the potato starch with one tablespoon of the sugar and the water. Bring to a boil then lower heat and simmer until thick. Remove from heat and cool.

Beat the egg whites in the electric mixer on high until soft peaks form. While the mixer is still beating, add the sugar spoonful by spoonful until it is all added.

Add the potato starch mixture slowly. Add the lemon juice. Continue to beat until stiff peaks form.

To Assemble:

Preheat the oven to 375 degrees.

All family members can help with the assembly of the lemon roll. Remove the cake roll from the refrigerator and unroll it so the towel is on the table. Gently spread the lemon filling over the area leaving a one-inch border empty. Roll up the cake roll, using the towel to help keep the cake even and being careful not to roll too tightly or the filling will ooze out.

Place the roll seam side down on a jelly roll pan. Spread the meringue evenly over the cake making any design you like. Brown in the oven for 8-10 minutes at 350 degrees. Turn off the oven and let stay for 2 or 3 minutes more if the browning is not too dark. If it is dark, remove immediately. Refrigerate until serving time.