Combine sugar and salt in a large bowl.

Stir in the egg until well combined.

Add the oil, buttermilk, and vanilla extract to the bowl and mix well.

Sift together the flour, baking powder, and baking soda.

Gradually add the dry ingredients to the wet ingredients, mixing after each addition.

Mix until a soft but not sticky dough forms.

Turn the dough out onto a lightly floured surface.

Roll the dough to 1/2 inch thickness.

Use a doughnut cutter to cut out the doughnuts.

Heat oil in a deep fryer to 370 degrees F (188 degrees C). Or test readiness by frying a bread cube which should turn golden brown in 60 seconds.

Carefully place the doughnuts into the hot oil.

Fry until golden brown, about 2-3 minutes per side, turning once.

Remove the doughnuts and place them on paper towels to drain excess oil.

Let the doughnuts cool slightly.

Dust with icing sugar or glaze with a butter icing glaze.