Preheat the oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan.
Mix dry ingredients: In a medium bowl, combine the flour, baking powder, baking soda, salt, and poppy seeds. Set aside.
Cream the butter and sugar: In a large bowl, beat together the softened butter and sugar until light and fluffy, about 3-4 minutes.
Add eggs and flavors: Beat in the eggs, one at a time, followed by the vanilla extract, lemon zest, and lemon juice.
Incorporate dry ingredients: Gradually add the dry ingredients to the wet ingredients in batches, alternating with the sour cream or yogurt, mixing just until combined.
Bake the cake: Pour the batter into the prepared loaf pan and smooth the top. Bake for 45-50 minutes, or until a toothpick inserted into the center comes out clean.
Prepare the glaze: While the cake cools, whisk together powdered sugar and lemon juice to make a glaze.
Glaze the cake: Once the cake has cooled for about 10 minutes, drizzle the glaze over the cake. Let it sit for another 10 minutes to set before slicing.