In a medium mixing bowl, whisk together flour, baking powder, and salt. Set aside.
In a large mixing bowl, whisk together the butter, sugar, eggs, sour cream, milk, lemon juice, zest, poppy seeds, vanilla, and almond extra until well combined.
Pour the dry ingredients into the wet. Fold until the flour is about halfway absorbed.
Pour in the blueberries and continue folding just until all of the flour is absorbed. The batter should be thick and fluffy. Cover with a towel and let the batter rest at room temperature for 1 hour. (Option: Rest overnight in the refrigerator.)
Preheat the oven to 425 degrees and line a 12 count muffin pan with paper liners. (Option: For taller muffins, only fill every other muffin cup (six total).) Once the batter has rested, do not stir. Gently scoop the batter into the prepared cups, filling them all the way to the top.
Bake the muffins for exactly 7 minutes. After 7 minutes and while the muffins are still in the oven, immediately reduce the temperature to 350 degrees. Bake for another 13-15 minutes or until a toothpick inserted in the center comes out mostly clean.
While the muffins bake, make the glaze. Whisk together the confectioners’ sugar and lemon juice until smooth.
Allow the muffins to cool for 5-10 minutes in the pan and then remove them. Drizzle each muffin with glaze.