Combine the raisins and grappa in a small bowl. Let them soak for at least 15 minutes, until plump.

Peel and dice the apples into 1 cm pieces while the raisins soak.

Whisk the flour, sugar, baking powder, and salt together in a large mixing bowl.

In a separate bowl, whisk the eggs and milk together, then pour into the dry ingredients and stir until just combined. The batter should be thick, like a pancake batter that barely drops off a spoon.

Fold in the diced apple, the soaked raisins along with any leftover grappa, and the lemon zest if using.

Pour the oil into a 26 cm / 10-inch heavy-bottomed skillet to a depth of about 3 cm. Heat to 175 C / 350 F, checking with a thermometer.

Drop tablespoons of batter into the oil in batches of 4 to 5, leaving space between each so they cook evenly and the oil temperature doesn't drop.

Fry for 2 to 3 minutes per side, until deep golden brown and cooked through in the center.

Lift fritters out with a slotted spoon and set on a wire rack over paper towels to drain. Let the oil come back to 175 C / 350 F between batches.

Let fritters cool 2 to 3 minutes, then dust generously with powdered sugar. Serve warm.