Blueberry muffins

Read through the recipe, gather the equipment, and use the ingredient lines to measure and prepare everything, drying the blueberries completely so they do not bleed or sink. Set the eggs on the counter so they lose their chill. Everything is measured and within reach.

Heat the oven to 425°F (220°C) with a rack in the middle position. Line the cups of the standard 12-cup muffin pan with the paper liners, then rub the flat top of the pan with the softened butter so the domes release. Start baking only after the oven reaches 425°F.

Melt the butter in the small saucepan over low heat, then take the pan off the heat and let the butter cool until it is liquid and just warm to the touch.

Put about 3/4 cup granulated sugar in the medium bowl and rub in the lemon zest, if using, with your fingertips until the sugar is damp and smells of lemon. Whisk in the melted butter, 1/2 tsp fine sea salt and the vanilla, then the sour cream and milk, until the base is smooth.

Taste the base before the eggs and flour go in, and eat a few blueberries too. Aim for sweet, rich and a little tangy, faintly salty and, with the zest, lemony. If it tastes flat, add fine sea salt to taste; if it tastes sharp, add granulated sugar to taste, no more than 1 tbsp for this batch. Whisk and taste again until the base tastes sweet, rich and gently tangy.

Whisk in the eggs one at a time until the base is smooth and glossy, with no streaks of white.

Whisk the flour, baking powder and baking soda in the large bowl. Pour in the wet base and fold with the rubber spatula, scooping from the bottom and turning the bowl, until only a few streaks of flour remain. Add the blueberries and keep folding gently just until no dry flour shows, stopping at the first purple streaks.

Fill the lined cups with heaping scoops from the 1/3-cup measure until each cup is filled almost to the rim, dividing the batter evenly. Sprinkle the turbinado sugar evenly over the tops, using all of it if the berries tasted tart and a little less if they were sweet.

Bake on the middle rack at 425°F until the tops begin to rise, about 5 minutes.

Turn the oven down to 375°F without opening the door, and keep baking on the middle rack until the muffins are domed and golden, the tops spring back when pressed lightly, and a toothpick pushed into the center of a muffin, not into a berry, comes out clean or with a few moist crumbs, about 13 to 18 minutes.

Cool the pan on the wire rack until you can touch the pan, about 5 minutes, then lift the muffins out onto the rack.

Divide the muffins into 12 servings, one muffin each, and serve them warm or at room temperature. Keep leftovers at room temperature in a container lined with paper towels for up to 2 days.