Stir the flour, ground almonds, 2 tablespoons of sugar, and baking powder together in the mug. Beat in the egg using a spoon.
Pour in the milk, oil, vanilla extract and lemon zest, and stir to a smooth batter.
Mix the lemon juice with 1 tablespoon of caster sugar and 1 tablespoon of boiling water. Pour over the top of the sponge.
Place the mug in the middle of the microwave and cook on high for 1½ –2 minutes, or until it has stopped rising and is just firm to the touch.
Spoon a dollop of creme fraiche on top of the cooked mug cake and watch as it melts into the middle of the hot sponge. Top with fresh raspberries.
Serve immediately.
