Preheat the oven to 160ºC/325ºF/gas mark 3. Butter a 20cm (8in) round cake tin and line the base with nonstick baking paper.
Place the raspberries and lemon juice into a mixing bowl. In another large bowl, whisk together the sugar and eggs until pale and thick, then carefully fold in the flour, baking powder and lemon zest. Gently stir in the butter.
Tip the batter into the tin then scatter in the raspberries and their juices. Sprinkle a little sugar over the top.
Bake for 1 hour, or until it springs back to the touch. Check halfway through the cooking time - you may find you need to cover the torta with foil to prevent the top from scorching. Allow to cool in the tin, then turn out.
Cooking tip
How to know when a cake is cooked - The cake will have an even colour, be firm yet springy to the touch and should be slightly shrinking away from the edges of the tin. Insert a clean skewer right down into the centre. If it comes out clean, the cake is cooked. After removing from the oven, give it a few minutes to rest in its tin before turning out on a cooling rack.
Topping alternative
Why not try using blackcurrants instead of raspberries for this recipe?
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This recipe is taken from Rays of Sunshine's first cookbook; A dish for a Wish. All the profits from the cookbook help the charity to continue granting magical wishes every day for seriously ill children.