Preheat the oven to 400 F. Lightly grease a baking sheet. Set aside. Mix together the flour, oatmeal, baking powder and baking soda, ground cardamom and salt in a large bowl. Using a pastry blender, cut in the cold butter until the mixture looks like coarse crumbs.
In another bowl, mix together the egg and yogurt until combined. Pour the egg mixture into the flour mixture and stir just until everything is moistened.
On a lightly floured surface, turn out the dough and gently knead it a few times until it comes together (10-12 times). Pat the dough to an 8-inch circle and cut into 8 wedges. In the prepared baking sheet, place the wedges about 2-inch apart and then transfer to the oven and bake for 12-14 minutes or until the scones look golden brown.
Transfer the scones to a wire rack and cool completely.
Stir together the powdered sugar and lemon juice until it is smooth and has a glaze consistency. Drizzle the lemon glaze over the cooled scones.