For the lemon cake, preheat the oven to 200 °C.
Beat the salt, sugar, eggs and grated lemon zest until fluffy. Add the whipped cream, then fold in the flour and baking powder. Finally, add the cooled butter as well as the rum flavoring and stir the whole thing into a light, fluffy dough.
Butter and flour a loaf pan well. Pour the batter into the pan and spread evenly. Bake in the heated oven for 7 minutes, then reduce the temperature to 180 °C and bake for another 30 minutes. Be sure to test the cake with chopsticks.
Remove the finished cake from the oven and turn it out of the pan on the spot. Place on a cooling rack. Drizzle with the remaining rum. Turn the oven temperature up to 250 °C. When the cake has cooled, brush the surface and sides with warmed apricot jam.
For the glaze, mix powdered sugar and lemon juice and empty onto the cake. Spread on sides with palette. Quickly place in very hot oven for 15 seconds to set frosting on lemon cake.