Heat the oven to 180°C and grease a muffin tin or put silicon muffin cases on a baking tray.
Mix the flour, ground almond Stevia/sugar and baking powder in a large mixing bowl. Stir in the lemon zest.
In a small bowl mix the melted butter, almond milk, eggs, lemon juice and vanilla extract. Pour the wet ingredients into the dry and mix with a wooden spoon until you get a smooth batter.
Spoon the batter into the muffin cups. Scatter the almond flakes on top.
Bake for 20 minutes until golden and an inserted skewer comes out clean.
Transfer them to a wire rack and let them cool.
Whisk the lemon juice and icing sugar until you get a thick but pourable icing. When the muffins are completely cool, drizzle the icing on top of them, letting it drip down their side.