Preheat the oven to 350F. Grease liberally and flour a bundt pan.

Toss the blueberries in the tbsp of flour.

Whisk all the dry ingredients together well. Add the cubed butter and mix until it resembles breadcrumbs.
Add eggs one at a time and beat till well incorporated. Add sour cream, lemon juice and zest, mix until just combined and the batter is smooth.
Carefully fold the blueberries into the batter.

Spoon the batter into prepared bundt pan and bake for 45-50min until a toothpick in the middle comes out clean. Cool in the pan for 15mins before carefully ineverting the cake onto a cook rack. Let cool completely.

Buttercream Frosting
Beat cream cheese, butter and vanilla with electric whisk on medium till light and fluffly.
Turn down to low and slowly add the icing sugar one cup at a time till fully mixed in. Turn up to medium high and beat till light and fluffly.

To decorate
With a medium round piping tip pipe the buttercream working across from inside to outside round the whole bundt.