Preheat the oven to 350 F (180 C) and prepare a muffin tin by placing paper cups inside.

Whisk the sugar and eggs with an electric mixer.
Add the butter a little at a time, continuing to whisk.
Incorporate the flour and pistachios, and mix gently until homogeneous.

Fill the cups halfway and bake for 15 to 20 minutes, or until a toothpick inserted into the center comes out clean.
Let cool for 10 minutes before removing from the tin and transferring to a cooling rack.

Heat the sugar and rum.
As soon as the sugar is melted and starts to brown, pour a little over the top of each cupcake.
Spread the glaze with a spatula over the cakes and decorate with some chopped pistachios.