Preheat your oven to 350°F (175°C) and grease a loaf pan.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large mixing bowl, cream the softened butter and granulated sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Stir in the sour cream, lemon zest, and lemon juice until just combined.
Gradually add the dry ingredient mixture to the wet ingredients, mixing until just combined.
Fold in the poppy seeds gently.
Pour the batter into the prepared loaf pan and smooth the top.
Bake for 50-60 minutes, or until a toothpick inserted comes out clean.
Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.
Dust with powdered sugar (optional) before serving.
