Put flour, salt and baking soda in a medium bowl and mix.
Add the butter and rub with your fingers. until it reaches breadcrumb consistency. Add the sugar and mix.
In a glass measuring cup, heat up the milk for about 30 seconds. Add vanilla and the squeeze of lemon juice, mix together and set aside.
Put the baking sheet in the oven and let it heat up while you finish making the scone.
Make a well in the middle of the dry mixture and add the milk mixture. Mix it together with a fork. When it’s starting to come together, mix it with your hand and gather all the flour together.
Lightly flour a clean surface. Dump the dough on top of it. Fold the dough 2-3 times and pat it into a smooth dough and about 4 cm thickness.
Dip the 5 cm round cookie cutter into some flour and push into the dough.
When you are running out of space in the dough, bring the dough together again and repeat step 7-8. You should have 12 scones.
In a small bowl, mix together the egg and milk. Brush the top of the scones with the egg wash.
Carefully put a sheet of parchment paper on top of the preheated baking sheet. Put the scones on the baking sheet. Bake for 10-12 minutes.