In a small bowl, soak the raisins in ¼ cup of the warm milk until plump and tender, about 15 minutes. Drain the raisins, reserving the milk.

Pour ¼ cup of the lukewarm water into a small bowl, add the yeast, the 1 teaspoon sugar, and the grappa, and stir to combine.

In a large bowl, combine the flour, the remaining ¼ cup sugar, the lemon zest, and salt and whisk until well mixed. Pour in the yeast mixture and stir until well blended.

Add the raisins and the reserved soaking milk along with the remaining 1 ¼ cups milk and 1 ¼ cups water and mix until you have a smooth, loose batter. Cover the bowl with plastic wrap and let the batter rise at room temperature for about 4 hours, giving it a gentle stir after the first hour and again after 3 hours.

Line a tray with paper towels and set it near the stove. Put the sugar and cinnamon in a large wide bowl, stir to mix, and set it near the stove.

Add about 4 inches oil to a medium pot (the pot should be tall enough that the oil won't overflow when you add the batter) and heat over medium-high heat (you can also use a deep fryer) to 350°F. When the oil is hot, scoop up 1 heaping tablespoon of the batter and carefully drop it into the oil. Add a few more doughnuts to the hot oil, but don't crowd the pot, or the temperature will drop too much. Fry the frittole, turning once, until they puff up and are golden on both sides, 3 to 5 minutes per side. Transfer to the paper towel-lined tray and continue cooking the frittole in small batches. (As you work, give the batter a stir from time to time to be sure the raisins are well distributed so you get a few in each frittole.) Once you've fried several frittole, put them in the bowl of cinnamon and sugar and roll until well coated, then transfer them to a plate and keep warm until serving.