Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper.

In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, baking soda, and salt.

Add the very cold, cubed butter and lemon zest to the dry ingredients. Use a pastry blender (or two forks, or your fingertips) to cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces of butter remaining. This is crucial for flaky biscuits.

In a separate small bowl, combine the cold buttermilk and 1 tablespoon of fresh lemon juice.

Pour the wet ingredients into the dry ingredients. Mix with a spoon or your hands just until everything is combined and a shaggy dough forms. Be careful not to overmix; overmixing develops gluten and makes biscuits tough.

Turn the dough out onto a lightly floured surface. Gently pat the dough into a roughly 3/4-inch thick rectangle. Fold the dough in half, then pat it down again to about 3/4-inch thickness. Repeat this folding and patting process 2-3 times. This layering technique helps create flaky biscuits.

Using a 2-inch biscuit cutter or a sharp knife, cut out biscuits. For a softer biscuit, place them close together on the prepared baking sheet. For crispier edges, space them further apart. Gather any scraps, gently re-pat the dough, and cut out more biscuits until all dough is used. Avoid overworking the scraps.

Bake for 12-15 minutes, or until the tops are golden brown and the biscuits are cooked through. Baking time may vary depending on your oven.

Transfer the baked biscuits to a wire rack to cool slightly.

While the biscuits cool, prepare the lemon glaze. In a small bowl, whisk together the powdered sugar, 2 tablespoons of fresh lemon juice, and optional lemon zest. Add more lemon juice a teaspoon at a time if needed, until the glaze reaches your desired consistency – thick enough to coat a spoon but thin enough to drizzle.

Once the biscuits have cooled for a few minutes but are still warm, drizzle or brush the lemon glaze over the tops. Let the glaze set slightly before serving.