1. Heat the oven to 180ºC (gas mark 4). Grease a 23cm (9in) spring-form cake tin and line the base with greaseproof paper.
2. Sift together the flour, baking powder and a pinch of salt.
Using an electric mixer, beat the butter, sugar and lemon zest for about 3-4 minutes, until well beaten, pale and fluffy. Beat in the eggs, one at a time, alternating with a little flour, until combined. With the machine on a low speed, mix in the remaining flour, alternating with the crème fraîche, until smooth.
3. Spoon the batter into the prepared cake tin and sprinkle the top of the mixture with
the blueberries.
4. To make the topping, rub
the butter into the flour and sugar until crumbly and then stir in the almonds.
Sprinkle the crumble mixture over the
top of the blueberries and press it down lightly.
5. Bake in the oven for about 1 hour, or until golden, risen and firm to the touch. A skewer inserted in the centre should come out clean. Allow to cool
in the tin for 10 minutes before removing it and placing on a
wire rack to cool completely.
Dust with icing sugar to serve.