In a small bowl, soak the raisins in the rum until the rum is absorbed (about 15 minutes).
Mix the egg yolk with vanilla, milk, lemon zest, and salt. Add flour and two tbsp of granulated sugar and mix well.
Beat egg whites until stiff and fold them into the batter.
Melt butter in pan that is large enough to fit all of the batter at once. The pancake should be fluffy, so make sure that the pan isn't so large that the batter spreads too thin.
Pour the batter into the pan, top with rum-soaked raisins, and then sprinkle with 1/2 tbsp granulated sugar. Cook until the bottom is brown. Flip the entire pancake over at once.
Continue cooking pancake until the batter is cooked all the way through. Once cooked, leave the pancake in the pan but use a spatula or a knife to shred the pancake into uneven bites.
Top the shredded pancake with powdered sugar and serve with a side of plum preserves. Serve warm in the pan.