Step 1Heat the oven to 325 degrees.
Step 2Blend 3/4 cup of the sugar and the oil in the bowl of an electric mixer. Add the egg yolks one at a time, beating after each addition. The mixture should be light yellow and fluffy.
Step 3Sift the matzo cake meal, potato starch and salt together. Add them to the yolk mixture alternately with the orange juice, lemon juice and orange and lemon zest.
Step 4Beat the egg whites in a bowl until soft peaks form; add the remaining 1/4 cup of sugar and beat until stiff enough to hold a peak. Fold the beaten egg whites into the egg yolk mixture. Pour the batter into a 10-inch tube pan.
Step 5Bake the cake until it is golden brown, it springs back to the touch, and a toothpick inserted in it comes out dry, 50 to 60 minutes. Remove the cake from the oven; immediately invert the pan and let it cool. Loosen the sides and center of the cake with a sharp knife and unmold it onto a cake plate.