Preheat the oven to 425F/220C and prepare a baking sheet/tray with either parchment paper or a silicone mat.
Put the flour, baking powder, salt and sugar in a large bowl and stir to mix.
Cut the butter into small chunks, add them to the flour mixture and rub them in with your hands by tossing the butter in the flour and rubbing the butter between your finger tips to break it into small pieces. Alternatively, use a pastry cutter. Either way, make sure you don't overwork the dough. You are looking for a breadcrumb-like texture.
Add the egg and milk (or cream, and vanilla, if using) to the flour-butter mixture and mix in to the dough, ideally with a blunt knife or a spatula to just combine everything. Add the raspberries (and lemon zest, if using) and carefully fold through the dough so they are reasonably well distributes but still stay in large pieces.
Turn the mixture out onto a floured surface and press it together. Flatten it out to around ⅔-1in/2-3cm thick. You can either cut the dough into 8 large square/rectangular scones, or 16 small scones (or triangles/ in-between sized as you prefer. I don't think this dough works as well with a cutter so just cutting shapes from the dough is best). Carefully transfer the scones to the prepared baking sheet.
Brush the top of the scones with egg wash or milk, if you like (it will help them go slightly browner on top). You could also sprinkle some sugar on top, though not really needed with the glaze.
Bake for around 10-12 minutes until gently brown on top. Allow to cool.
Once cool, mix together the confectioner's sugar, lemon juice and zest to form a smooth paste. Drizzle over the top of the scones.