Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan with non-stick spray or butter, then dust with flour.

In a medium bowl, combine the all-purpose flour, poppy seeds, baking powder, baking soda, and salt. Whisk to combine and set aside.

In a large mixing bowl, cream the softened butter and sugar with an electric mixer on medium speed for 3-4 minutes until light and fluffy.

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

Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk. Stir gently until just combined.

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

Bake in the preheated oven for 50-60 minutes or until a toothpick inserted in the center comes out clean.

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