Mix the flour, baking powder, and salt in a small bowl and set aside.
In a medium bowl, mix together the oil, yogurt, and granulated sugar. Mix well to combine. Add in the egg and mix again.
To this, add the vanilla, zest, and lime juice. Mixing to combine, but not overmixing.
Combine the wet ingredients and the dry ingredients. Be careful not to overmix.
I like to use a piping bag to fill the donut pan, especially since I use mini donut pans. It will take 1-2 tablespoons of batter per donut.
Place into the preheated oven and bake for 6 minutes for mini donuts and about 10 for regular-sized donuts.
Once they are baked, gently turn out the donuts onto a wire rack.