Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.

In a mixing bowl, whisk together the flour, baking powder, sugar, and salt.

Cut in the cold butter using a pastry cutter until the mixture resembles coarse crumbs.

Gently fold in the diced rhubarb.

In another bowl, whisk together the cream and egg. Add to the dry ingredients and mix until just combined.

Turn the dough onto a floured surface and pat into a circle about 1 inch thick.

Cut into wedges and place on the prepared baking sheet.

Bake for 15-20 minutes or until golden brown.

In a small bowl, combine powdered sugar, lemon juice, and lemon zest until smooth.

Drizzle the glaze over the warm scones once they are out of the oven.