Preheat your oven to 425°F (220°C).
Line baking sheet with parchment paper.
Sift gluten-free flour, baking powder, and salt together.
Add sugar to the flour mixture.
Cut cold butter into small cubes.
Rub butter into flour until mixture resembles breadcrumbs.
Beat egg with milk and vanilla extract.
Make a well in the flour mixture.
Pour wet ingredients into the well gradually.
Mix gently until dough just comes together.
Turn dough onto lightly floured surface.
Pat dough to 1-inch thickness gently.
Cut straight down with cookie cutter.
Place scones on prepared baking sheet.
Brush tops with milk for golden color.
Bake for 12-15 minutes until golden brown.
Cool on wire rack before serving.