Soak the almonds in warm water for at least three hours before starting the recipe. Drain them well and blend them together with the lemon juice and zest, oil, rum, vanilla, and “lemon drops” until you achieve a fine and smooth cream. Slice the lemons thinly, removing any seeds, and set them aside. Crack the eggs and separate the yolks from the whites. Beat the egg whites to stiff peaks with an electric mixer, along with a pinch of salt. Whisk the yolks with the sugar until you have a light and frothy mixture. Combine the almond cream with the yolks and mix well; once fully incorporated, gently fold in the egg whites, adding them little by little with movements from top to bottom to avoid deflating the batter. Arrange the lemon slices at the bottom of the mold (I chose a silicone mold, so no greasing was needed), then pour the batter on top. Bake in a preheated oven at 170°C (338°F) for about 35 minutes. Remove from the oven, let cool, and turn out onto a serving plate.