Creating the Classic Blueberry Buckle is both fun and easy. Follow these steps for a delicious dessert:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease and flour a 9×13-inch baking dish.
2. Mix Butter and Sugar: In a large bowl, cream together the granulated sugar and ½ cup softened butter until light and fluffy.
3. Add Eggs and Vanilla: Beat in the eggs, one at a time, followed by the vanilla extract, mixing well.
4. Combine Dry Ingredients: In another bowl, whisk together 2 cups of flour, baking powder, and salt.
5. Mix Dry and Wet: Gradually add the dry ingredients to the creamed mixture, alternating with the milk. Stir until just combined.
6. Fold in Blueberries: Gently fold in the fresh blueberries (and lemon zest if using) until evenly distributed.
7. Prepare the Streusel: In a small bowl, mix ½ cup flour, brown sugar, and cinnamon. Cut in ¼ cup softened butter until crumbly.
8. Pour Batter: Spread the batter evenly into the prepared baking dish. Sprinkle the streusel topping over the batter.
9. Bake: Place in the oven and bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
10. Cool: Once baked, allow it to cool in the dish for about 10-15 minutes before slicing.