Preheat oven to 350°F (175°C). Grease and flour a 9×5-inch loaf pan or line it with parchment paper.

In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.

In a large bowl, beat softened butter and sugar until light and fluffy (3-4 minutes).

Add eggs one at a time, then mix in vanilla extract, lemon zest, and lemon juice until combined.

Alternate adding the dry ingredients and sour cream to the butter mixture, starting and ending with dry ingredients. Mix just until combined.

In a separate bowl, beat together cream cheese, sugar, egg, and vanilla until smooth.

Pour half of the lemon batter into the prepared loaf pan. Spread cream cheese mixture evenly over batter, avoiding edges. Pour remaining batter on top and smooth the surface gently.

Bake for 50–60 minutes or until a toothpick inserted near the center comes out mostly clean. Cool in pan 10–15 minutes, then transfer to a wire rack to cool completely.