Step 1

Preheat oven to 350°. Soak raisin in rum in a small bowl for 30 minutes. Strain, reserving rum and raisins separately.

Step 2

Using an electric mixer, beat egg yolks, 1/2 cup milk, flour, sour cream, and salt in a medium bowl until smooth. Beat in vanilla, zests, remaining 1/2 cup milk, 1 tsp. reserved rum.

Step 3

Place egg whites in another medium bowl. Using clean, dry beaters, beat whites until foamy, about 1 minute. Add 1 tbsp. sugar and beat until white and thickened. Add another 1 tbsp. of sugar and beat until soft peaks form. Gently fold egg whites into flour mixture.

Step 4

Melt 1 tbsp. butter in a 10” cast-iron or heavy ovenproof skillet over medium-low heat; pour in batter. Do not stir. Cook until edges start to set, 5–7 minutes. Transfer to oven. Bake until pancake is puffed and cooked through, 20–25 minutes.

Step 5

Slide pancake onto a work surface; cut into 1” pieces. Melt 2 Tbsp. butter in same skillet over medium-high heat. Add 2 tbsp. sugar, half of raisins, and half of lemon juice. Add half of pancake pieces and cook, turning occassionally, until glazed and golden, about 5 minutes. Transfer to a platter. Repeat with remaining 2 tbsp. butter, 2 tbsp. sugar, raisins, lemon juice, and pancake pieces. Add to platter and dust with powdered sugar.