Making the Classic Blueberry Buckle is easy if you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 375°F (190°C) and grease a 9-inch round or square baking pan.
2. Mix Dry Ingredients: In a large bowl, whisk together the flour, sugar, baking powder, and salt.
3. Cream Butter: In another bowl, cream the softened butter until light and fluffy.
4. Add Egg and Vanilla: Mix in the egg and vanilla extract, combining well.
5. Combine Mixtures: Gradually add the flour mixture to the butter mixture, alternating with the milk. Stir until just combined.
6. Fold in Blueberries: Gently fold in the blueberries and lemon juice if using.
7. Prepare the Batter: Pour the batter into the prepared baking pan, spreading it evenly.
8. Make Streusel Topping: In a separate bowl, combine the flour, sugar, and cinnamon for the streusel. Drizzle in the melted butter and mix until crumbly.
9. Add Topping: Sprinkle the streusel mixture evenly over the batter.
10. Bake: Place the pan in the preheated oven and bake for 40-45 minutes or until a toothpick inserted in the center comes out clean.
11. Cool: Once baked, remove the buckle from the oven and let it cool in the pan for 10-15 minutes before transferring it to a wire rack.

These straightforward steps will guide you in creating this amazing Classic Blueberry Buckle that everyone will love!