Preheat your oven to 400˚F (200˚C). Prepare a large baking sheet by lining it with parchment paper or lightly greasing it to prevent sticking.
In a large mixing bowl, combine the all-purpose flour, granulated sugar, baking powder, Meyer lemon zest, and salt. Stir until well mixed.
Quickly cut in the chilled and diced unsalted butter until blended, ensuring no pieces are larger than a pea for optimal flakiness.
In a separate medium bowl, whisk together heavy cream, egg, Meyer lemon juice, and vanilla extract until fully combined. Pour this mixture into your dry ingredients and gently combine until it just comes together without overmixing.
Transfer the dough onto a floured surface and lightly knead it just enough to bring it together into a disc about 3/4 inches thick. Cut into eight equal slices and transfer them to your prepared baking sheet, placing them about 1/2 inch apart before brushing their tops with cream.
Place the baking sheet in your preheated oven and bake until the tops turn golden brown, which should take about 12 minutes. Once baked, let them cool for five minutes before transferring them to a wire rack to cool completely.