Place the butter, sugar, flour, ground almonds and cinnamon in a food processor and 'pulse' until mixture begins to resemble a soft paste. Add the egg, a little at a time, to bind the ingredients together.
Divide the mixture in two parts, making one a little larger than the other. Press the larger amount into the base of the tin. Set aside 150g of the berries to make the sauce.
Put the remaining 350g on top of the torte mixture in the tin, in an even layer, keeping them away from the outside edge. Take the remaining, smaller amount of paste and shape it into a rough round about the size of the tin. Cover the fruit with this, pushing the torte mixture gently to reach the sides of the tin. The finished surface will look quite rough and uneven, but this is how it should be.
Place the torte tin on top of a flat baking sheet and put it in the centre of a moderate oven. (Gas Mark 5, 190C, 375F) Bake for up to 45 minutes until dark golden brown and firm to touch.
Remove and cool slightly in the tin, before dusting with icing sugar.
To make the fruit sauce, put the 150g berries that were set aside into a blender, together with 1 tbsp caster sugar and the juice of half a lemon. Liquidise until smooth.
Pour into a fine sieve sitting over a clean bowl and press the liquidised fruit through the sieve, with the back of a wooden spoon, to remove any traces of pips and skin.
The sauce should taste sharp, but add a little more sugar, if you prefer it sweeter. Transfer the finished sauce into a container suitable for serving. The sauce could be warmed gently, if preferred.
