Step 1

Preheat oven to 325 degrees. Butter two 5-by-9-inch loaf pans. Combine 3 1/4 cups flour and salt in a bowl.

Step 2

Cream butter, sour cream, and sugar with a mixer on high speed until pale and fluffy, for 8 minutes. Scrape down sides of bowl. Reduce speed to medium, and add vanilla extract.

Step 3

Lightly beat eggs, and add to mixer bowl in 4 additions, mixing thoroughly after each and scraping down sides. Reduce speed to low, and add flour mixture in 4 additions, mixing until just incorporated. Toss blueberries in remaining 2 tablespoons flour; fold into finished batter. Divide batter between pans. Tap on counter to distribute; smooth tops.

Step 4

Before baking, sprinkle sanding sugar over each cake. Bake until a tester inserted into center of each cake comes out clean, about 65 minutes. Let cool in pans on a wire rack for 30 minutes. Remove from pans, and let cool completely on wire rack.

Step 5

Make the lemon cream: Combine heavy cream, confectioners' sugar, and lemon zest in a bowl. Beat until soft peaks form.