Preheat your oven to 375°F (190°C) and prepare a muffin tin with liners.
In a large bowl, mix together the flour, baking powder, and salt. In another bowl, cream together the butter and granulated sugar until light and fluffy. Beat in the eggs, lemon zest, lemon juice, milk, and vanilla extract. Gradually add the dry ingredients to the wet ingredients and mix until just combined.
For the crumb topping, mix the flour, granulated sugar, brown sugar, melted butter, and cinnamon in a separate bowl until crumbly.
Fill the muffin tin with the batter and sprinkle the crumb topping over each muffin. Bake for 18-20 minutes or until a toothpick comes out clean.
Let the muffins cool in the tin for a few minutes before transferring to a wire rack.
For the glaze, whisk together the powdered sugar and lemon juice until smooth. Drizzle over the cooled muffins.
Notes
These muffins are best served warm. You can store them in an airtight container for up to 3 days.