Butter and flour 2 (8-inch) round cake tins. Preheat the oven to 350 degrees F.
In a medium bowl, add salt, baking powder and flour. Stir with a fork to mix well.
In a mixing bowl, beat the oil and sugar together, then add the eggs, 1 at a time, beating thoroughly after each addition. Put the dry ingredients in a sifter and sift about 1/3 into the egg mixture. Fold in the flour and zest, then add about 1/3 of the milk. Continue with the remaining third of flour and milk until all the ingredients have been incorporated and blended together.
Pour the batter into prepared cake tins, place in the preheated oven, and bake for 25 minutes, or until cakes are set, pull away from the sides of the pan, and spring back when pressed lightly in the center with a finger.
Remove cakes from the oven, and turn the cakes out, onto cooling racks. When cool, spread marmalade or jam between the layers and press layers together. Sprinkle top of cake with powdered sugar.
Pear Marmalade (Marmellata di Pere):
In a large bowl, mix fruit and sugar together thoroughly, cover with a kitchen towel, and set aside for at least 3 hours to let the juices start to run. Transfer to a large nonreactive saucepan and cook over moderate to medium-low heat until pears are heated through, about 10 minutes stirring with a wooden spoon to prevent sticking. Remove from heat when mixture is dense.
Yield: 3 cups