Heat oven to 400°F. Line a baking sheet with parchment.
Whisk flour, sugar, baking powder, salt, and lemon zest in a large bowl.
Cut in cold butter until pea-sized bits remain and mixture looks sandy.
Stir cream, lemon juice, and vanilla together in a measuring cup.
Make a well. Add liquids. Mix with a fork just until shaggy.
Turn dough onto a floured surface. Fold gently 6–8 times to bring together.
Pat into a 7-inch round, about 1 inch thick. Cut into 8 wedges.
Set wedges on sheet. Brush tops with cream and sprinkle with sanding sugar.
Bake 13–16 minutes until edges are golden. Cool on the pan 10 minutes.
Whisk powdered sugar, lemon juice, and cream until smooth and pourable.
Drizzle glaze over warm scones. Let set briefly before serving.