Preheat your oven to 350°F and grease two mini loaf pans and line with parchment paper.
In a small bowl, whisk together flour, baking powder, and salt. Set aside.
In a medium bowl, combine softened butter, shortening, and sugar. Beat until light and fluffy, 1 to 2 minutes.
Beat in eggs one at a time, followed by lemon juice and zest.
Add half of the flour mixture, mixing until just combined, repeating with all of the milk and then the rest of the flour mixture.
Divide batter between baking pans and bake for 28 to 35 minutes, until a toothpick inserted into the center of the cakes comes out clean.
Cool before adding the glaze.