Preheat your oven to 180°C (350°F) and line your muffin tin with paper liners or lightly grease it.
In a large bowl, whisk together the flour, sugar, baking powder, and salt until evenly combined. This creates a light, airy dry base for your muffins.
In a separate bowl, pour in the melted butter and whisk in the eggs until the mixture is frothy and slightly pale. Add the milk, vanilla, and lemon zest if using, and stir until smooth.
Pour the wet ingredients into the dry ingredients and gently fold together with a spatula just until combined. Avoid overmixing to keep the muffins tender and fluffy.
Toss the blueberries in a little flour to prevent sinking, then gently fold them into the batter, distributing evenly but being careful not to crush the berries.
Spoon the batter into the prepared muffin cups, filling each about ¾ full. Sprinkle a little extra sugar on top for a crispy, sweet crust.
Bake in the preheated oven for 20-25 minutes, or until the muffins are golden brown and a toothpick inserted in the center comes out clean. You’ll hear a gentle sizzle and see the tops turn a warm, inviting hue.
Remove the muffins from the oven and let them cool in the tin for about 5 minutes. Then, transfer to a wire rack to cool slightly and allow the flavors to settle.
Once cooled a bit, serve these muffins warm or at room temperature. The tops should be slightly crispy, with a moist crumb inside that’s bursting with juicy blueberries.
