Place a cooling rack over a sheet pan.
Place about 1 cup (200 grams) sugar in a wide plate for coating the fritters. Set aside.
Place the Quark in a mixing bowl and whisk in the eggs.
Then whisk in the 1/4 cup plus 2 tablespoons of sugar, the salt, vanilla, and zest, if using.
In a separate bowl, whisk together the flour and baking powder.
Switching to a wooden spoon, beat in the flour mixture just until well-combined. Don't overmix. Set aside.
Pour the oil into a medium pot and set over medium-high heat. Bring the oil to 350˚F (180˚C). When the oil is at the right temperature, regulate the heat to keep the temperature steady.
Using an ice cream scoop, scoop five fritters into the pot.
Let them cook, turning once, for 3 to 4 minutes. They should be golden brown all over. If they are browning too quickly, that is a sign that the oil is too hot.
Using a spider or fork, remove the fritters carefully from the oil and place on the cooling rack just for a moment while you portion the next round of fritters and place them in the oil.
While the second round of fritters is in the oil, roll the first batch of fritters in the bowl of sugar.
Put the sugared fritters back on the cooling rack.
Repeat with the remaining batter and sugar.