Preheat your oven to 350°F (175°C). Line a 9″x5″x3″ loaf pan with parchment paper, ensuring it covers all sides.

1. Mix dry ingredients: In a medium bowl, sift together 1.5 cups of all-purpose flour, 1 tsp baking powder, and 1/4 tsp baking soda. Set aside.
2. Mix wet ingredients: In another bowl, combine 1/2 cup melted butter, 3 eggs, and 1 cup sugar. Add 1 tsp lemon zest, 1 tsp lemon extract, and 1 pack of vanilla sugar (or 1/2 tsp vanilla extract). Mix thoroughly for about 2 minutes until well combined.
3. In a small bowl, toss 1 cup of fresh blueberries with 1 tbsp of flour. This helps to keep the blueberries evenly distributed throughout the loaf.
4. Gradually add half of the flour mixture to the egg mixture, mixing until just combined.
5. Add 1/2 cup of sour cream and mix until incorporated. Add the remaining flour mixture and continue to mix until all ingredients are blended.
6. Gently fold the flour-coated blueberries into the batter, ensuring even distribution.
7. Pour the batter into the prepared loaf pan, spreading it evenly. Bake in the preheated oven for 55 minutes. To check for doneness, insert a knife into the center of the loaf. If it comes out clean, the loaf is baked to perfection.
8. Prepare the icing: In a small bowl, mix 1/2 cup powdered sugar with 2 tbsp melted butter and 2 tbsp fresh lemon juice until smooth.
9. Once the loaf is completely cool, spread the icing evenly over the top. Let the icing set before slicing.
10. Enjoy!