Preheat the oven to 425 degrees. Place liners in each cup of a muffin pan. Set aside.
In a medium mixing bowl, combine flour, sugar, poppy seeds, baking powder, and salt and set it aside.
In a large mixing bowl, beat together milk, butter, egg, and lemon juice.
Mix dry ingredients slowly into the wet ingredients until just incorporated, along with the lemon zest. Fill each cavity in the muffin pan and set aside.
In a small bowl combine flour, sugar and lemon zest for the crumble. Add butter and mix until crumbly. Sprinkle crumble on top of the batter in each cavity.
Bake in the oven at 425 for 5 minutes then decrease the temperature to 350 and bake for an additional 15 minutes.
Notes
Store in an airtight container on the counter for 3-5 days.
Freeze in a ziplock bag for up to three months, and allow to thaw to room temperature before eating.
You can chill the batter overnight and bake in the morning - this will even help make them slightly fluffier.