Preheat your oven to 425°F. Place a 9x13 inch baking dish (or similar size) in the oven with the full 1/2 cup of salted butter to melt as the oven heats. This will take about 10 minutes and gives you time to prepare your dry ingredients. The butter will be ready to use once the oven reaches temperature.

While the oven heats, whisk together the flour, granulated sugar, baking powder, lemon zest, salt, baking soda, and ground cardamom in a large bowl. This ensures the leavening agents and spices are evenly distributed throughout the flour, which will give your biscuits consistent rise and flavor. I like to add the cardamom here because it blooms beautifully when mixed with the other dry ingredients.

Pour the room temperature buttermilk into the dry ingredients from Step 2 and stir until just combined. The mixture will be thick and somewhat shaggy—don't overmix or your biscuits will be tough. Once the oven reaches 425°F and the butter is melted, remove the baking dish from the oven and carefully pour 4 tablespoons of the melted butter from the dish into the dough, stirring gently to incorporate it. Reserve the remaining butter in the dish.

Gently fold the fresh blueberries into the dough from Step 3, being careful not to crush them or overmix. Spread the dough evenly into the hot baking dish with the reserved melted butter, letting the butter coat the bottom and help the biscuits cook beautifully. Sprinkle the turbinado sugar over the top—this creates a delightful crunch and caramelizes slightly during baking. I find that using your hands or the back of a spoon to gently spread the dough works better than a spatula, which can crush the blueberries.

Bake the biscuits at 425°F for 25 minutes, until the top is golden brown and a toothpick inserted into a biscuit comes out clean. Remove from the oven and let rest for 5 minutes—this allows the crumb to set slightly without the biscuits becoming dry. Cut into 9 equal pieces and serve warm.