How to make
Beat 1 cup (225 g) of the butter with the baking powder, brown sugar, flour, eggs and half the orange rinds into a smooth mixture.
Pour the mixture into an 8″ (20 cm) form and bake in a preheated 360°F (180 °C) oven until ready. Once it cools completely, cut it into 2 equally thick layers.
For the butter glaze, beat the rest of the butter with the powdered sugar and remaining orange rinds into a light cream. Make the syrup by heating the orange juice and sugar on low heat.
Stir until the mixture is reduced by half. Put the first layer in a platter and pour half the syrup over it.
Smear it with half the glaze and cover with the second layer. Syrup it as well and smear it with the remaining glaze. Sprinkle with grated orange rinds. Consume right away or store in the fridge.
