Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper or a silicone mat—cold surfaces help the biscuits puff up nicely.

In a large bowl, whisk flour, baking powder, sugar and salt until evenly blended—no clumps.

Drop in the cold butter cubes, then use a pastry cutter (or two forks) to work the butter into the flour until the mixture resembles coarse crumbs, pea-sized bits are perfect. Don’t overmix; you want little butter pockets to steam.

In a separate bowl, whisk the buttermilk (plus lemon zest and juice, if using). Pour wet into dry, folding gently with a spatula until the dough just comes together—shaggy and sticky is fine.

Toss blueberries in a tablespoon of flour—this keeps them from sinking and bleeding too much color. Fold them in softly.

Turn dough onto a lightly floured surface. Press into a 1-inch thick rectangle (about 8×6 in). For extra flaky layers, fold the dough in half, press gently, then roll again to 1-inch thickness. Use a 2½-inch biscuit cutter to cut rounds, pressing straight down (no twisting). Reroll scraps once to get 2–3 more biscuits.

Place biscuits about 1 inch apart on the sheet. Brush tops with a little buttermilk or melted butter for a golden finish; sprinkle sugar for a touch of sparkle. Bake 12–15 minutes until tops are golden and bottoms are lightly tan—a toothpick should come out clean.

Rest 5 minutes on the pan, then transfer to a wire rack. Serve warm with honey, jam, or just plain—they’re a lovely sweet treat as is.