Prepare Your Baking Dish: Preheat your oven to 180°C (160°C fan/Gas Mark 4). Lightly grease and flour a 23cm (9-inch) square baking dish or a similar sized round dish. The oven will begin to warm, filling your kitchen with a subtle, dry heat.

Combine Dry Ingredients: In a large mixing bowl, whisk together the plain flour, 150g caster sugar, baking powder, bicarbonate of soda, and salt. Ensure there are no lumps and the mixture looks uniformly pale and fluffy.

Mix Wet Ingredients: In a separate medium bowl, whisk the lemon zest, lemon juice, buttermilk, vegetable oil, egg, and vanilla extract until well combined and the mixture is a light, creamy yellow. You should detect the uplifting, citrusy aroma of the lemon.

Combine Wet and Dry: Pour the wet ingredients into the dry ingredients. Stir gently with a spoon or spatula until just combined. Be careful not to overmix; a few small lumps are perfectly fine. The batter will be thick and shaggy.

Fold in Blueberries: Gently fold in the blueberries. If using frozen, there's no need to thaw them, but they might release a bit more colour into the batter. The batter will take on a lovely speckled appearance, with the deep purple-blue berries distributed throughout.

Bake the Dessert: Pour the batter evenly into your prepared baking dish. Sprinkle the remaining 2 tablespoons of caster sugar over the top. This will create a lovely, slightly crisp, caramelised crust. Place in the preheated oven and bake for 35-40 minutes. The dessert is ready when a skewer inserted into the centre comes out clean, and the top is golden brown with a delightful, sweet, cooked fruit aroma wafting through your kitchen.

Cool and Glaze (Optional): Let the dessert cool in the dish on a wire rack for at least 15-20 minutes before attempting to slice. If you’re making the glaze, whisk the icing sugar and lemon juice until smooth. Once the dessert has cooled slightly, drizzle the glaze over the top for an extra burst of lemon flavour and a beautiful finish. The glaze will set with a slightly opaque, glossy appearance.