Spongy yeast cake soaked in rum syrup until gloriously moist is Neapolitan pastry perfection. This iconic mediterranean dessert is a family tradition in Naples.
In a mixing bowl, combine instant yeast, warm milk, and 1 tablespoon of sugar; let sit for 10 minutes until bubbly to activate the yeast.
Add eggs and melted butter to the bowl, whisk well; then add flour, the remaining sugar, salt, and lemon zest, mixing until you get a sticky dough.
Knead the dough on medium speed for 7–8 minutes until smooth and elastic, then cover and let rise in a warm spot until doubled, about 1.5 hours.
Transfer dough into well-buttered babà molds or a bundt pan, cover, and proof again until the dough nearly reaches the rim, about 40 minutes.
Bake in a preheated oven at 350°F (175°C) for 25–30 minutes until deep golden brown; test with a skewer for doneness, then unmold onto a rack.
While cakes cool, prepare rum syrup by heating water, sugar, and lemon zest over medium heat until syrupy, 6–8 minutes; remove from heat, then stir in dark rum after it cools slightly.
Soak cooled babà thoroughly by pouring or dipping in warm rum syrup, allowing them to absorb fully for ultimate moistness—repeat if necessary.
Serve slightly warm or at room temperature, optionally brushing with extra syrup right before serving for added shine and flavor.