Preheat the oven to 425 degrees. Line a large baking sheet with parchment paper. Combine flour, ½ cup granulated sugar, baking powder, baking soda, cinnamon, and salt in a medium bowl. Cut in butter with a pastry blender or 2 knives until the mixture resembles coarse crumbs. In a separate bowl whisk together 1 cup buttermilk, egg yolk, and vanilla extract and stir into flour mixture until just moistened.
Turn dough out onto a lightly floured surface and gently knead 4 to 5 times with floured hands. Gently pat dough to ¾-inch thickness. Using a 3-inch-round biscuit cutter, cut out 8 shortcakes, gathering scraps and patting out again if necessary, and transfer to the prepared baking sheet. Brush tops of shortcakes with remaining 2 tablespoons buttermilk and sprinkle with 2 teaspoons sugar.
Bake shortcakes until lightly golden, 12 to 14 minutes. Cool on the baking sheet on a wire rack 10 minutes. Carefully split shortcakes horizontally using a serrated knife.
Hull and chop 15 strawberries and toss in a bowl with 2 teaspoons sugar; set aside. Combine heavy cream, confectioners' sugar, and orange zest in a bowl and beat with an electric hand mixer on high until stiff peaks almost form. Refrigerate until ready to use. Hull and halve 20 berries lengthwise. Hull and vertically slice 8 strawberries. Use any remaining strawberries for garnish or reserve for another use.
Place the bottom halves of shortcakes, cut side up, on eight serving plates and spread each with 2 tablespoons whipped cream. Arrange 5 strawberry halves, on their sides (with the cut side facing in towards the center) around the edge of each shortcake to form a ring. Spoon chopped strawberries into the center of the ring. Top with 2 tablespoons whipped cream and place shortcake tops, cut side down, on top. Spread tops with 1 tablespoon whipped cream, leaving a ½-inch border. Decoratively arrange 4 to 5 strawberry slices on top and sprinkle with remaining 1 teaspoon sugar. Drop a small dollop of whipped cream in the center of sliced berries and garnish with the orange zest strips if using. Serve or refrigerate until ready to serve.