Preheat the oven to 375ºF.

Line a baking sheet with parchment paper.

First make the raspberry jam: In a small saucepan, combine the raspberries, sugar, lemon juice, and salt.

Bring to a boil over high heat, stirring until the sugar has dissolved.

Skim off any light-colored foam around the sides and discard.

Cook, stirring occasionally, until thickened and the temperature reaches 220ºF, 12 to 15 minutes.

Remove from the heat.

Strain through a fine-mesh sieve to remove some or all of the seeds, if desired.

Ladle into a mason jar and cool completely.

Make the scones: In a large bowl, combine the cake flour, baking powder, baking soda, salt, and granulated sugar.

Add the butter and, using a pastry blender or your fingers, blend the butter into the flour until it is in pea-size pieces.

Create a well in the center of the bowl and add the eggs, buttermilk, and vanilla.

Using a fork, mix the ingredients until they are just combined into a shaggy dough.

Add the currants, if using, and knead until combined.

Lightly flour a work surface and roll the dough out into a 1-inch-thick round using a rolling pin.

Cut into 8 wedges.

Put the wedges on the prepared baking sheet.

Brush with buttermilk and sprinkle with raw sugar.

Bake for 20 to 25 minutes, until golden brown and crisp.

Serve warm, with the raspberry jam.