Step 1: Preheat your oven to 400°F (200°C). Pour the melted butter into a 9x9 inch baking dish, ensuring the bottom is evenly coated.
Step 2: In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt.
Step 3: Pour the milk into the dry ingredients. Stir with a spoon or spatula until just combined. The dough will be very wet and sticky. Gently fold in the blueberries until evenly distributed.
Step 4: Carefully pour the wet biscuit dough over the melted butter in the baking dish. Do not stir or mix. Spread the dough gently to the edges of the pan using a spatula, being careful not to disturb the butter too much.
Step 5: Using a sharp knife or bench scraper, score the top of the dough into 9 equal squares. Do not cut all the way through, just score the surface. This helps with even baking and easy separation later.
Step 6: Bake for 25-30 minutes, or until the biscuits are golden brown on top and cooked through. A toothpick inserted into the center should come out clean.
Step 7: While the biscuits are baking, prepare the lemon glaze. In a small bowl, whisk together the powdered sugar, lemon juice, and lemon zest until smooth. Add more lemon juice a teaspoon at a time if you prefer a thinner glaze.
Step 8: Once the biscuits are out of the oven, immediately drizzle the lemon glaze generously over the warm biscuits. The warmth will allow the glaze to melt slightly and soak into the nooks and crannies.
Step 9: Let the biscuits cool slightly before serving. Use a knife or spatula to separate them along the scored lines. Enjoy warm!