You can eat this cake plain, but my favorite way is with strawberries or raspberries macerated for a short time (30 minutes is fine) with a little sugar and topped with cream softly whipped and lightly flavored with Mathilde Orange Liqueur X.O. This is a liqueur I favor over Grand Marnier. It is softly orange with a slight somewhat caramel flavor, making it good to use as an ingredient and lovely to drink on its own.
Clothilde is French and bakes by weight, and I recommend that when you make this cake, you weigh the ingredients too. Just to see if it makes a difference, if you have a scale, measure one cup flour by the scoop-and-level method without compressing the flour, then weigh it and see if it weighs the same 120 grams called for in the directions.
Clothilde calls this cake Le Piege Gateau.
Orange Sponge Cake
Adapted from the blog Chocolate & Zucchini
For a 9-Inch Cake Pan (not springform):
1 large pat butter
1 heaping tablespoon sugar
For the Cake:
120 grams (1/2 cup plus 1 tablespoon) unsalted butter, softened
120 grams (1/2 cup plus 2 tablespoons) sugar (I use Florida Crystals organic)
2 large eggs
1 medium organic orange, scrubbed well since you will use the peel
120 grams (1 cup) flour
1 tablespoon baking powder
A pinch of salt
Preheat the oven to 350 degrees. Cream the butter with the sugar, then add the eggs one by one, mixing after the addition of each egg until completely combined.
Without going into the pith, grate the zest from the entire orange over the bowl. This is easy if you use the original Microplane grater; one pass over the orange will do it. Juice the orange, and add 1/2 cup of the juice to the batter. Mix until smooth.
Put the flour, baking powder, and salt together in a small bowl. Stir with a fork, then sift the contents of a bowl onto a piece of aluminum foil. Pick up the foil, making a sort-of spout to "pour" the ingredients from, and whisk this dry mixture into the batter until just combined. Put the batter into the prepared 9-inch cake pan.
Bake in the preheated oven for 20 minutes or until the cake is golden brown and starts to pull away from the sides of the pan. Let cool on a rack for ten minutes - but no more than this or the caramel crust the sugar has made, which is one of the delights of this cake, will harden and stick to the pan.
Turn onto a serving plate, and let cool completely before serving.