Preheat the oven to 180°C. Line cupcake pan with liners and keep it ready.
Combine all the dry ingredients from flour to salt in a bowl and mix well.
Combine all the wet ingredients which are egg, buttermilk, oil, and vanilla in another bowl. And mix with an electric mixer until combined.
Add the wet mixture to the dry mixture and mix well until combined. Do not overmix.
Add hot water to this and mix immediately, scraping the sides of the bowl. You will get a thin batter.
Pour this batter into the liners only half way full and bake for 18-20 minutes until a toothpick inserted comes out clean. It is okay if the toothpick inserted comes out with only few moist crumbs attached.
Cool completely before frosting.