Preheat oven to 350 degrees F. Coat a loaf pan with oil.
In a mixing bowl, beat the butter, brown sugar; until light and fluffy. Add in the eggs, vanilla extract, lemon extract, oil and buttermilk; stir to combine.
In a small mixing bowl, mix together 2 cups flour, baking powder and salt. Mix the dry ingredients into the wet ingredients, mixing until just about combined. Toss the blueberries with the remaining 1 tbsp of flour and add to the batter, mixing until just combined.
Pour the batter into the prepared loaf pan. Sprinkle evenly with 1 tbsp sugar and 1 tbsp rolled oats. Bake for 50-60 minutes; or until a toothpick inserted in the center comes out clean. Let cool completely before removing from the pan.