This single serving lemon blueberry muffin is soft with sweet blueberries and a tangy lemon glaze. Fresh lemon flavors both the muffin and the glaze for a bright citrus finish.
Preheat the oven to 400°F (200°C). Lightly grease a 10-ounce ramekin and set it on a small baking sheet.
In a medium bowl, whisk the melted butter and sugar together until combined.
Whisk in the egg yolk until the mixture is smooth.
Whisk in the lemon zest, vanilla, milk, and lemon juice until the batter is smooth.
In a small bowl, stir together the flour, baking powder, and salt.
Add the dry ingredients to the wet ingredients and stir gently just until no streaks of flour remain.
Fold in the blueberries, keeping them whole.
Pour the batter into the prepared ramekin and spread the top even.
Bake for 15 minutes, until the top is golden and a toothpick inserted in the center comes out clean.
Let the muffin cool completely on a wire rack.
Make the glaze: Whisk the powdered sugar and lemon juice together until smooth, then drizzle the glaze over the cooled muffin.
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Notes
Use a 10-ounce ramekin. This recipe is tested for a 10-ounce ramekin about 4.3 inches wide and 2.4 inches tall. A larger or smaller vessel will change the bake time.Zest the lemon before juicing it. Once the lemon is cut and juiced, the surface is too soft and wet to zest cleanly. Zest first while the lemon is whole and dry, then cut and squeeze for the juice.Check that your baking powder is fresh. Baking powder is the only leavener in this recipe. To test it, stir ¼ teaspoon into ½ cup of hot water; if it bubbles right away, it's still good.Don't overmix the batter. Stir just until no streaks of flour remain, then stop. Mixing past that point develops gluten and makes the crumb tough.Bake on a rimmed baking sheet. Set the ramekin on a small rimmed baking sheet before it goes in the oven. It makes the ramekin easier to move in and out and catches any drips from the batter.Add the glaze once the muffin is cool. A warm muffin causes the glaze to melt and run off the sides instead of setting on top.If doubling this recipe, double the ingredients and use either two 10-ounce ramekins or one 5x5-inch baking dish.