In a mixing bowl, whisk together the flour, baking powder, salt, and granulated sugar.
In a separate bowl, beat the eggs, then add the milk and vanilla extract. Mix until well combined.
Gradually add the wet ingredients to the dry ingredients, whisking continuously until a smooth batter forms.
Heat vegetable oil in a heavy-bottomed pot or deep fryer to 375°F (190°C). Use a cooking thermometer to ensure the oil is at the right temperature.
Using a small ice cream scoop or tablespoon, carefully drop spoonfuls of the batter into the hot oil, avoiding overcrowding. Fry in batches if necessary.
Fry the zeppole fritters until golden brown, turning them occasionally to ensure even cooking. This should take about 2-3 minutes per batch.
Using a slotted spoon or spider strainer, carefully remove the fried fritters from the oil and transfer them to a plate lined with paper towels to drain excess oil.
Allow the zeppole fritters to cool slightly before dusting them generously with powdered sugar. Serve warm.