Preheat your oven to 350°F (175°C). Grease and flour the loaf pan or line it with parchment paper for easy removal.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.
Add the eggs one at a time, mixing well after each addition. Then stir in the vanilla extract and citrus zests (lemon and orange).
In a separate bowl, combine the all-purpose flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, alternating with the milk. Mix until just combined.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake in the preheated oven for 50 minutes, or until a toothpick inserted into the center comes out clean.
Remove the loaf cake from the oven and let it cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.
While the cake cools, prepare the glaze. In a small bowl, mix the powdered sugar and lemon juice until smooth. Adjust the consistency with more lemon juice or powdered sugar as needed.
Once the loaf cake is completely cool, drizzle the glaze over the top and allow it to set for a few minutes before slicing.