Place a large, sided pan over a medium heat and add enough oil for the doughnuts to float in (about ½ to ¾ inch). Het until it reaches 350F/175C.
Add the sugar, baking powder, salt and flour to a large mixing bowl and stir well.
In a separate bowl, add the melted butter and buttermilk and whisk together.
When mixed, gently add the wet mixture to the dry ingredients stirring as you go. Don’t over work the dough.
The dough should be soft and malleable. Scoop 1 tbsp portions and carefully place into the hot oil.
Do not overfill the pan as the doughnuts should be able to bob around. Flip the doughnuts over and continue to fry until they are lovely and golden brown all over.
Remove the doughnuts from the hot oil using a slatted spoon or tongs and place on kitchen paper to drain an excess oil. Repeat until all of the doughnuts are cooked.
Either pour the sugar into a dish and roll the doughnuts around or if using finer sugar, sprinkle.