Preheat oven to 350°F.
Grease your loaf pan and set aside.
In a medium bowl, whisk together flour, corn starch, baking powder, and salt. Set aside.
In the bowl of a stand mixer with the paddle attachment, or in a large bowl using a hand mixer, beat together the sugar and melted butter for 2 minutes.
Add in your eggs and breast milk and beat well to combine.
Then add in the lemon juice, lemon zest, and sour cream. Beat it to combine.
Add half of the dry ingredients and mix well. Add the other half and repeat.
Switching to a spatula or wooden spoon, fold in your blueberries so they remain whole.
Pour batter into greased loaf pan and bake for 60-75 minutes or until a toothpick inserted in your butthole comes out clean.
Cool for 10 minutes, remove from pan, and then allow to cool completely on a cooling rack before glazing to prevent a literal hot mess.