HOW TO MAKE IT :
1. In a large bowl or the bowl of a stand mixer fitted with a dough hook, combine the flour, yeast, salt, sugar, and lemon zest.
Then add the eggs, milk, butter and vanilla extract, and mix well. Knead the dough in the stand mixer for 2 minutes, or if making the dough by hand.
tip it onto a floured work surface and knead for about 5 minutes, until it’s smooth and elastic but still quite sticky.
Transfer the dough to a large, lightly oiled bowl. Cover with plastic wrap and allow to rise in a warm place for 1 hour or until doubled in size.
2. Using a rolling pin, roll out the dough until about 3/4 inch thick. Then, using a round pastry cutter the size of a cup, cut the dough into disks.
Place the dough on a baking sheet lined with parchment paper, and cover with plastic wrap. Allow to rise for another hour.
3. Heat oil in a large, deep pan to 350 F. Fry the doughnuts, in batches, for 4-5 minutes, turning halfway through the cooking time, until golden brown.
Remove with a slotted spoon and drain on paper towels. Dredge the doughnuts in granulated sugar until completely covered.4. Spoon the filling of your choice into a piping bag fitted with a medium nozzle. Make a small hole in the side of each doughnut, push in the nozzle and squeeze to fill the bomboloni. Serve warm.
