Preheat oven to 350°F (175°C) and grease mini bundt pan well.
In a bowl, whisk together flour, baking powder, and salt.
In another bowl, beat butter and sugar until fluffy. Add eggs, then lemon zest, juice, and vanilla.
Add flour mixture and buttermilk alternately, beginning and ending with flour. Stir just to combine.
Fill bundt cavities ¾ full and bake for 18–22 minutes.
Let cool in pan for 10 minutes before removing to wire rack.
Mix powdered sugar and lemon juice to make glaze.
Drizzle glaze over cooled cakes. Add zest on top if desired.
