Make the cream by heating the milk with the sugar, vanillas and rind of the orange to boiling point, then lower the heat to a minimum. Separately, beat the eggs with the flour so it doesn't become too thick, add a few extra tbsp of milk.
Remove the orange rind and vanilla pod, pour the egg mixture in a thin trickle. Stir until the cream thickens but don't increase the heat because the egg whites will curdle. Add the rum and butter. Leave the prepared cream to cool a bit, stirring occasionally so it doesn't catch a crust.
In the meantime, start making the dough. Sift the flour and baking powder in a bowl. Beat the eggs with the sugar and pour it into the flour mixture, along with the oil and lemon juice. Knead a smooth dough but don't knead too long - just enough to blend the products until smooth.
Divide it into 2 balls - 1 larger than the other. Roll out the larger one on a floured counter to a round sheet, relatively thin, with a diameter at least 1 1/4″ (3 cm) greater than the form in which you'll be baking. Place the sheet in it after greasing it and covering it with baking paper. Press the edges that are sticking out firmly to the walls of the form.
Pour on the cream and cover with the remaining dough after rolling it out to a thin sheet as well (sprinkle extra flour during rolling because it'd be quite sticky otherwise and the sheet would break when you try to unstick it from the counter).
Sprinkle pine nuts and put in a preheated 365°F (185 °C) oven for 30-35 min. or to a golden crisp.
Once the cake cools, sprinkle with powdered sugar.