Preheat oven to 350°F and prepare three 9-inch cake pans. (I just use the baking spray with flour in it, but use whatever method you like best.)
Beat the 1 cup butter on high until smooth and creamy. Add the 1¼ cups granulated sugar and ½ cup light brown sugar. Continue to beat until well creamed.
Add the 4 eggs and 1 Tablespoon vanilla extract and beat on medium until completely incorporated.
In a separate bowl, whisk together the 3 cups all-purpose flour, 1 Tablespoon baking powder and ½ teaspoon salt. Stir into the wet ingredients until just incorporated.
Add the 1 cup buttermilk and 7 Tablespoons lemon juice and stir until it just comes together.
Toss 1½ cups blueberries with the extra 1 Tablespoon all-purpose flour and fold into the batter.
Spoon into prepared pans (about 3 cups per pan) and bake for 20-25 minutes (add a little time if you are baking in a 9×13). The sides should be just pulling away from the edge of the pan and if you insert a toothpick in the center it should come out clean.
Let cakes cool in their pans for about 5 minutes and then invert onto cooling racks. Allow to cool completely before frosting.
Cream Cheese Frosting
Beat together 8 ounces cream cheese and ½ cup butter until smooth.
Add 3½ cups powdered sugar, 1 pinch salt, 2 Tablespoon heavy cream and the 1 teaspoon vanilla extract. Mix on low until the sugar is well incorporated, then turn mixer to high. Beat for 2-3 minutes then add additional cream until you have the desired consistency.
Layer the cakes and frosting on your serving tray. End with a healthy dose of frosting and garnish with blueberries if desired.
Notes
You can use a cup of milk soured with a teaspoon of lemon juice in place of the buttermilk.