Step 1: Prep
Preheat oven to 350°F (175°C).
Grease and line two 9-inch round cake pans (or one 9x13-inch pan) with parchment paper.
Toss blueberries with 1 tablespoon flour and set aside.
Step 2: Mix Dry Ingredients
In a bowl, whisk together flour, baking powder, baking soda, and salt.
Step 3: Cream Butter & Sugar
In a large bowl, beat butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition.
Mix in lemon zest and vanilla extract.
Step 4: Combine
Alternate adding dry ingredients and buttermilk to the butter mixture, beginning and ending with dry ingredients.
Mix until just combined — do not overmix.
Gently fold in floured blueberries.
Step 5: Bake
Divide batter evenly between pans and smooth tops.
Bake 30–35 minutes (round pans) or 40–45 minutes (9x13 pan).
Cake is done when a toothpick inserted in center comes out clean.
Cool in pans for 10 minutes, then transfer to a wire rack to cool completely.
Step 6: Glaze (Optional)
Whisk powdered sugar and lemon juice until smooth.
Drizzle over completely cooled cake.
Let glaze set before slicing.