Heat enough oil to fill a medium pot about 1-inch full over medium-high heat until the oil is about 370 degrees F.
In a large mixing bowl, whisk together the flour, baking powder, lemon zest, and salt.
In a medium mixing bowl, whisk together the ricotta, eggs, sugar, and vanilla until smooth.
Add ricotta mixture to flour mixture and whisk to combine. The dough will thicken and be very sticky.
Working in batches, use a small cookie scoop to drop batter into the hot oil.
Fry until the fritters are golden brown, about 1-2 minutes, turning once. Remove cooked fritters from the oil with a spider strainer (or slotted spoon) and place on a paper towel-lined plate. Repeat until all batter has been fried.
Sprinkle the top of the fritters with more lemon zest, and sprinkle with powdered sugar. Serve warm with blackberry preserves.
If you don't fry the fritters long enough, the center will still be some and may have some raw batter. Don't be afraid to let them get a rich golden brown color to ensure they're cooked all the way.You can always open a fritter up and check the inside to test if you're frying them long enough.