Beat soft butter for 20 seconds in a large bowl with electric beaters or a stand mixer with the paddle attachment.
Add sugar gradually while you continue beating at medium speed, and then for 3 more minutes after adding all of it. The mixture should be light in color, fluffy and the sugar will have partially dissolved.
Add the eggs, one at a time, beating well after each addition. Make sure to scrape the sides of the bowl regularly.
Add vanilla, lemon zest, lemon juice and mix. It might look curdled, but don't worry.
Remove and reserve 1 tablespoon of the flour. Sift the rest with the dry ingredients (flour, salt and baking powder) together in a bowl, or have them measured and sift them directly over the cake batter.
Add them in 2 parts, alternating with the cream cheese in 1 part. That means you start and end with the dry ingredients.
Mix and integrate it well, but don't beat much at this point. After adding the last part of the flour mixture, you should have most of it not incorporated when you add the berries. After adding the flour, cake batters should not be beaten too much as that will develop gluten and toughen the baked cake.
Toss blueberries with the reserved tablespoon of flour, add to the batter and combine with a spatula. Make sure everything is incorporated, but try not to crush the blueberries. There should be no flour spots, but some specks around the berries are fine. You should have a thick, smooth batter with berries.
Pour the batter into the prepared pan and smooth the top.
Bake in the middle rack for about 45 minutes, until it rises, the top cracks and a tester inserted in the middle comes out clean. Pound cakes are dense so make sure it's fully baked. If the top is browning too quickly but the middle is not done, cover it loosely with a piece of aluminum paper and continue to bake.
Cool on a wire rack and remove carefully from the pan, removing the strip of paper.
Drizzle the glaze over and let it dry before cutting and eating.
Keep leftovers at room temperature for a day or two or in the refrigerator for several days, with plastic wrap in both cases, or frozen for a month, well wrapped also.