Step 1

Stir together strawberries, lemon zest, lemon juice, and 1⁄2 cup of the granulated sugar in a medium bowl. Cover; refrigerate at least 30 minutes or up to 1 hour.

Step 2

Preheat oven to 425°F. Whisk together flour, baking powder, baking soda, salt, and remaining 2 tablespoons granulated sugar in a large bowl. Cut in butter with a pastry blender (or use fingertips) until mixture resembles peas. Add buttermilk, and stir gently with a spatula or wooden spoon until well combined and shaggy. Turn out dough onto a lightly floured surface, and knead gently until dough just comes together, 2 to 3 times. Pat dough with lightly floured palms to 1 1⁄2-inch thickness (do not use a rolling pin). Cut out biscuits using a 2 1⁄2-inch round cutter, gathering and patting scraps once more to make 12 biscuits.

Step 3

Place biscuits about 2 inches apart on a parchment paper-lined baking sheet. Refrigerate 30 minutes. Brush tops of biscuits with 2 tablespoons of the heavy cream; sprinkle with sanding sugar. Bake in preheated oven until golden brown, 18 to 20 minutes. Cool on baking sheet 10 minutes.

Step 4

Place powdered sugar in bowl of an electric stand mixer fitted with whisk attachment. Scrape vanilla bean seeds into powdered sugar; add remaining 2 cups heavy cream. Beat on medium speed until soft peaks form, 4 to 5 minutes. Split biscuits; place on plates or a large platter. Spoon strawberry mixture onto bottom halves of biscuits. Dollop with whipped cream; cover with biscuit tops.