Preheat your oven to 350°F (175°C).

Generously grease your mini Bundt pans with butter or cooking spray.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until well combined.

In another bowl, combine melted unsalted butter, buttermilk, eggs, lemon juice, and lemon zest. Stir until fully blended.

Gradually add the wet ingredients to the dry ingredients, mixing gently until just combined, then fold in the poppy seeds.

Pour the batter into the prepared mini Bundt pans, filling each about 2/3 full.

Bake for approximately 20 minutes, or until a toothpick inserted comes out clean.

Allow the cakes to cool in the pans for about 5 minutes before removing them to a wire rack.

In a small bowl, mix together powdered sugar and lemon juice until smooth. Drizzle over the cooled cakes.