GET ORGANIZED: Preheat oven temperature to 350F/176.7C. Spray an 8.5 x 4.5 x 2.5 inch loaf pan (21 x 11 x 6 cm) with cooking spray (or grease with butter) and dust with flour. Zest one large lemon and set aside (and a zest a second lemon to sprinkle on the finished loaf if you like).
COMBINE DRY INGREDIENTS: (except sugar) Whisk together flour, baking powder and salt in large mixing bowl.
1 1/2 cups all-purpose flour, Note 1, 2 teaspoon baking powder, 1/2 teaspoon salt
COMBINE WET INGREDIENTS AND SUGAR: In a medium separate bowl, whisk sour cream eggs, sugar, lemon zest, vanilla and oil until smooth.
1 cup sour cream, 1 cup sugar, 3 large eggs, 1 tablespoon lemon zest, 1/2 teaspoon vanilla extract, 1/2 cup vegetable or canola oil
COMBINE INGREDIENTS FROM BOTH BOWLS: Add wet mixture to dry ingredients and combine with whisk just until flour disappears. Don't overmix or the loaf will be dense. Gently fold in the blueberries dusted in flour with a spatula.
BAKE: Pour batter into greased/floured prepared pan. Bake on middle rack for about 50-70 minutes. A glass loaf pan will take longer than metal. Since ovens vary, start checking at 50 minutes. If toothpick or tester inserted into center of loaf comes out clean, it's done. Cool cake for 10 minutes on rack, then remove cake from loaf pan and place it on rack, top facing up, over a pan or cutting board (something to catch any drips if you are add the lemon syrup).
MAKE AND ADD LEMON SYRUP (OPTIONAL): For an even moister, more lemony loaf, poke holes in top of cake with tester or toothpick. Pour on lemon syrup to soak in. Let loaf cool completely on a wire rack.
MAKE AND ADD GLAZE: Mix together icing sugar and fresh lemon juice in a small bowl. After the loaf cools, drizzle glaze over cake. Sprinkle with lemon zest if desired. Slice and serve.