Preheat oven to 325 degrees F. In a medium bowl, combine flour, baking soda and salt. Set aside. Prepare a 10" tube or bundt pan by greasing, throughly, and dusting well with powder. Set aside.
In a large mixing bowl, beat butter and sugar until light and fluffy, approximately 2-3 minutes. Add in eggs, one at a time, beating well after each addition. Add in lemon juice and zest and beat well. Scrape down bowl to make sure all ingredients are well combined.
With mixer on low speed, add in 1/2 of dry ingredients and mix until just combined. Add in half of buttermilk, and mix until just combined. Repeat.
Toss blueberries in flour to coat, then gently fold into the cake batter. Scoop batter into prepared pan. Bake for approximately 65-75 minutes, or until a cake tester inserted into cake comes out clean, and cake bounces back when lightly pressed.
Allow to cool slightly, then use a spatula or knife to gently loosen the cake from the sides of the pan. Then allow cake to continue to cool for approximately 10 minutes. Once cooled, invert cake onto a cake plate or pan. Allow to cool completely.
To make frosting, combine frosting ingredients in a bowl and mix until smooth. Drizzle over cake.
Store tightly covered.