Whisk egg yolks, vegetable oil, and 1 cup sugar in a bowl until thoroughly combined; stir matzo cake meal and potato starch into egg yolk mixture to make a workable dough. Press dough into an 11x17-inch baking pan. Transfer apricot jam to a bowl and stir until spreadable; spoon jam onto crust and spread in an even layer.
Bake in the preheated oven for 10 minutes.
Beat egg whites in a bowl until frothy, using an electric mixer. Gradually beat in 1 cup sugar and cinnamon until meringue forms glossy, sharp peaks. Fold walnuts into meringue and spread over jam layer, covering jam and crust completely.
Return to oven and bake until meringue is lightly golden brown and crust is set, about 20 more minutes. Let cool completely before cutting into squares with a sharp knife. As you cut, you might want to wash the sharp knife every once in awhile, as the meringue sticks to the knife.
