Prepare Your Oven and Tray: Preheat your oven to 220°C (200°C fan). Line a large baking tray with baking parchment.

Combine Dry Ingredients: In a large mixing bowl, whisk together the plain flour, bicarbonate of soda, cream of tartar, caster sugar, and salt. This helps to aerate the flour.

Rub in the Butter: Add the cold, cubed butter to the flour mixture. Using your fingertips, rub the butter into the flour until the mixture resembles coarse breadcrumbs with a few larger, pea-sized pieces of butter remaining. This is a crucial step known as the rubbing in method, which creates a light texture.

Add Flavourings: Stir the lemon zest through the flour and butter mixture. Gently fold in the raspberries, being careful not to break them up too much. If using frozen raspberries, add them straight from the freezer.

Form the Dough: Make a well in the centre of your mixture and pour in the cold buttermilk. Use a palette knife or a fork to bring everything together into a soft, slightly shaggy dough. Don't overmix! What works best for me is to stop as soon as it just comes together.

Shape and Cut: Tip the dough out onto a lightly floured surface. Gently bring it together with your hands and lightly knead just 2-3 times to make it smooth. Pat the dough out into a circle about 4cm thick. Use a large, sharp knife to cut the circle into 8 equal wedges.

Prepare for Baking: Carefully place the wedges onto your prepared baking tray, leaving a little space between them. Brush the tops with the beaten egg, which will give them a lovely golden-brown finish.

Bake to Perfection: Bake for 12-15 minutes, or until the scones are well-risen and a beautiful golden brown on top. Transfer them to a wire rack to cool completely.

Make the Glaze: While the scones are cooling, make the glaze. In a small bowl, whisk the sifted icing sugar with 2 tablespoons of lemon juice until you have a smooth, drizzly consistency. Add a little more lemon juice if it's too thick.

Garnish and Serve: Once the scones are completely cool, drizzle the lemon glaze over the top. Allow the glaze to set for a few minutes before serving.