1. For the shortcakes, preheat the oven to 200°C. Line a large baking sheet with parchment.
2. Combine the flour, granulated sugar, baking powder and salt in a large bowl. Add the butter and work it into the flour mixture with your fingers until it resembles coarse meal.
3. Whisk together the lemon zest, egg and 1/2 cup of the buttermilk in a small bowl. Add to the flour mixture and lightly mix with your hands or a spoon until the dough just comes together. Do not overmix. Turn the dough out onto a lightly floured work surface. With lightly floured hands, gently pat the dough into a 7inch round about 1/2 inch thick. Cut into 8 equal wedges. Space the shortcakes evenly on the prepared baking sheet. Brush the tops with the remaining 1 tablespoon buttermilk and sprinkle with the almonds. Bake until golden brown, 12 to 15 minutes.
4. For the filling, combine the strawberries, granulated sugar and orange zest and juice in a large bowl. Let stand until the sugar is dissolved and the mixture is syrupy, about 15 minutes.
5. Split the shortcakes. Place the bottom halves of the shortcakes on plates and top evenly with the strawberry mixture and yogurt. Cover with the shortcake tops. Dust with the confectioners' sugar if using.