Preheat Oven – Set to 350°F (175°C). Line muffin tin.
Mix Dry Ingredients – Whisk flour, baking powder, and salt.
Cream Butter Mix – Beat butter, sugar, and lemon zest until fluffy.
Add Eggs & Vanilla – Mix in eggs one at a time, then vanilla.
Combine with Milk – Add dry mix in 3 parts, alternating with milk.
Stir in Lemon Juice – Mix gently until just combined.
Fold in Blueberries – Toss blueberries with a little flour, then fold in.
Bake – Fill liners ⅔ full. Bake 18–20 mins.
Cool – Rest 5 mins in tin, then cool on a rack.