Preheat your oven to 350°F (175°C) and grease a loaf pan.
In a mixing bowl, combine flour, baking powder, and salt.
In another bowl, beat the butter and sugar until creamy. Add eggs, milk, lemon juice, lemon zest, and vanilla extract. Mix well.
Gradually add the dry ingredients to the wet mixture and stir until just combined.
In a separate bowl, blend cream cheese, sugar, egg, and vanilla until smooth.
Pour half of the lemon batter into the loaf pan. Add cream cheese mixture on top, then pour the remaining lemon batter over it. Swirl gently with a knife.
Bake for 50 minutes or until a toothpick inserted in the center comes out clean.
Let it cool in the pan for 10 minutes before transferring to a wire rack.
Notes
For extra lemon flavor, add more lemon zest. You can also glaze the bread with a lemon glaze after baking.