Preheat the oven to 325 degrees F. Line two muffin tins with 15 cupcake liners.
Add the vanilla seeds to the milk and set aside.
Pass the flour and baking powder through a fine-mesh sieve into a medium bowl. Whisk in the salt and set aside. In a stand mixer fitted with the paddle attachment, beat together butter and sugar until pale and fluffy. One at a time, add the eggs, beating until combined. Gently add the flour mixture in two batches, alternating with the milk mixture. Remove the bowl from the mixer and fold in the moscato.
Divide the batter among the cupcake liners, filling each by two-thirds. Bake, rotating halfway through, until golden brown and a toothpick comes out clean, about 20 minutes. Transfer to a wire rack to cool.
Pipe the buttercream onto the cupcakes in a rose pattern, dust with white luster, and finish with an edible pearl.
Place the egg whites and sugar in the bowl of stand mixer. Set the bowl over a pot of gently simmering water and heat, stirring with a wooden spoon, until the sugar has dissolved and is warm to the touch (about 160 degrees F). When you touch the mixture, it should feel completely smooth and not at all gritty.
Immediately transfer the bowl to a stand mixer fitted with the whisk attachment. On high speed, whip until glossy and stiff, about 15 minutes.
Switch to the paddle attachment and lower the speed to medium. Add the butter, piece by piece, incorporating each before adding more. Lower the speed further and mix until silky and smooth.