Strawberry Biscuit Sheet Cake

Name: Strawberry Biscuit Sheet Cake
Ingredients: 4 cups cake flour (not self-rising), such as Swans Down, plus more for dusting; ⅔ cup granulated sugar; 5 teaspoons baking powder; 2 teaspoons kosher salt; 1 ½ sticks cold unsalted butter, cut into pieces; 1 ¼ cups buttermilk; Heavy cream, for brushing; Fine sanding sugar, for sprinkling (optional); 4 cups sliced strawberries (from 2 quart containers); 5 tablespoons granulated sugar; ¼ teaspoon kosher salt; 2 teaspoons fresh lemon juice; 1 ¼ cups heavy cream; Scraped seeds from 1 vanilla bean, or 2 teaspoons pure vanilla paste; 3 tablespoons confectioners’ sugar; Freeze-dried strawberries, finely ground, for serving (optional)