In a large mixing bowl, combine the flour, granulated sugar, baking powder, and salt. Mix well.
In a separate bowl, beat the eggs lightly. Add the olive oil, milk, and lemon zest. Whisk together until well combined.
Pour the wet ingredients into the bowl with the dry ingredients. Stir until a dough starts to form. Use your hands to knead the dough until it becomes smooth and elastic.
Cover the dough with plastic wrap and let it rest for about 30 minutes.
After the resting period, take small portions of the dough and roll them into thin ropes, about 1/2 inch thick. Join the ends of each rope to form a ring shape. Repeat until all the dough is used.
In a deep pot or skillet, heat vegetable oil over medium heat. The oil should be about 2 inches deep.
Carefully place a few rosquillas into the hot oil and fry until they turn golden brown on both sides. Make sure to flip them halfway through for even cooking. Remove the fried rosquillas using a slotted spoon and place them on a paper towel-lined plate to absorb any excess oil. Repeat until all the rosquillas are fried.
Once the rosquillas have cooled slightly, prepare the glaze. In a small bowl, whisk together powdered sugar and lemon juice until you get a smooth, pourable consistency.
Dip each rosquilla into the glaze, ensuring they are well coated. Place them on a wire rack or a plate to allow the glaze to set.
Let the rosquillas sit for about 15-20 minutes until the glaze hardens. They are now ready to be enjoyed!