Step 1: Prep and Prevent Sinking
Preheat the oven to 350°F and lightly grease a 9×5-inch baking dish. In a small bowl, toss the blueberries with 1/4 cup of flour.
Why this works: Coating the blueberries in flour adds friction, helping them stay suspended in the batter instead of sinking to the bottom during baking.
Step 2: Cream the Base
In a large bowl, cream the butter, 1 cup of sugar, and lemon zest together for 3–5 minutes, until pale, light, and fluffy. Beat in the egg and vanilla until fully incorporated.
Step 3: Combine Dry Ingredients
In a separate bowl, whisk together the remaining flour, baking powder, salt, and cinnamon if using.
Step 4: Alternate Mixing
Add the dry ingredients and buttermilk to the butter mixture in alternating additions—beginning and ending with the dry ingredients—to create a smooth, stable batter.
Step 5: Fold and Bake
Gently fold the floured blueberries into the batter. Pour into the prepared pan and sprinkle the remaining tablespoon of sugar over the top for a lightly crisp finish. Bake for 40–50 minutes, until a toothpick inserted comes out clean.
Step 6: Cool and Slice
Allow the cake to cool on a wire rack for at least 15 minutes before slicing. This resting time helps the crumb set and prevents the blueberries from bleeding into the cake.
