Preheat the oven to 180°C top/bottom heat. Line the muffin tray with muffin liners.
For the muffin batter, cream the butter with the icing sugar and vanilla paste, add the grated lemon zest and beat with the eggs until fluffy.
Mix the flour with the baking powder and stir in the lemon juice. If the dough becomes too dry/thick, add milk to thin it out. However, the dough should still be firm.
Fold in the frozen raspberries with a dough scraper.
Divide the batter between the muffin liners.
For the crumble topping, rub the flour, cold butter in small pieces, sugar and cinnamon together between your hands. Divide between the muffin liners.
Bake the muffins in the oven on the middle shelf for approx. 20 minutes.Then leave to cool. When the muffins are cool, mix the icing sugar with as little lemon juice as possible to make the glaze. The glaze should be runny but as thick as possible.Drizzle the glaze over the muffins with a spoon.
