Preheat the oven to 180°C.
Mix the flour with the baking powder, then add the sugar and lemon zest.
Mix the eggs with the vanilla and oil. Add the lemon juice to the yoghurt, then add this to the egg mixture. Add this to the flour, combining gently.
Fold in the blackberries and flaked almonds, if used.
Spoon the batter into a silicon muffin case or a muffin tin, lined with paper baskets.
Bake for about 20-25 minutes in the oven until golden brown and an inserted skewer comes out clean.
Let the muffins cool in their cases for 5 minutes, then transfer them to a wire rack to cool completely.
When cooled, serve or decorate them to your liking.