Add the ricotta, eggs, lemon zest, sugar, vanilla, and salt to a large bowl. Whisk until combined.
Whisk in baking powder.
Gently whisk in flour until combined. Cover the bowl with a kitchen cloth while you´re heating up the oil.
Heat the oil in a medium/large pot until 350°F (175°C).
Scoop the batter with an ice cream scoop into the oil. Don´t add too much batter at once or the temperature of the oil will drop quickly.
Cook the doughnuts in batches, for about 3-4 minutes, turning them once on the other side, until golden brown in color.
Transfer with a spider strainer or a slotted spoon to a plate lined with paper towels.
Let cool until just slightly warm them roll in superfine or powdered sugar until coated on all sides.
Enjoy!