Sift together flour, baking powder, and salt in a bowl. Set aside.
Whisk together the eggs and 3 tablespoons of sugar. Add ricotta, lemon zest and vanilla and stir until combined. Do not over mix.
Gradually add the flour mixture to the ricotta mixture and stir until smooth. Set aside.
Combine the remaining 1/2 cup of sugar and cinnamon in a small bowl and set aside.
Heat the oil in a medium saucepan over medium-high heat until hot and faint streaks appear on the bottom of the pan. Working in batches, carefully drop 1 tablespoon of dough at a time into the oil and fry, turning several times, until golden brown. Adjust the heat as necessary to prevent burning fritters.
Drain on paper towels or brown paper bag. Toss the warm fritters in the cinnamon sugar mixture.
Cut the corner off of a jelly filled pastry bag and fill each zeppole with jelly.