Preheat your oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.

In a large mixing bowl, cream together the softened butter and sugar until light and fluffy.

Add the eggs, one at a time, mixing well after each addition. Then stir in the vanilla extract and lemon zest.

In a separate bowl, whisk together the flour, baking powder, and salt.

Gradually add the dry ingredients to the butter mixture, alternating with the milk. Start and end with the dry ingredients. Mix until just combined.

Stir in the fresh lemon juice until evenly distributed.

Pour the batter into the prepared baking pan and smooth the top with a spatula.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.