Preheat the oven to 180c and line the baking tin with parchment, making it easy to lift out the cake at the end of baking.
Begin by making up the flaxseed mixture. Place the ground flaxseed in a small bowl with 6 tablespoons of water, stir together and set aside to thicken up – these will replace the eggs in your baking, helping the mixture to bind together. Next, peel and trim the carrots before coarsely grating – you’ll want to do this by hand as using a food processor to grate the carrots will leave them, and the cake, soggy. Peel and core the apple and then cut into slim slices. Finely chop the dried apricots.
Place the margarine in a large mixing bowl, add the sugar and cream together with a wooden spoon until, light, combined and incorporated. Stir in the flaxseed mixture until mixed through and then sift in the flour, baking powder and mixed spice. Add the grated carrots, apricots and raisins to the mixture and fold in until well mixed.
Spoon the mixture into the lined tin and spread out, using the back of a spoon to level the top. Scatter the apple slices over the top of the traybake and then, using the flat of your hand, gently press them down slightly into the mixture. Bake in the oven for 35 – 40 minutes until golden and fragrant. Remove from the oven and leave to cool for a few minutes in the tin. While still warm, brush the top of the slices with the apricot jam and then transfer to a wire rack to cool completely. When ready, cut into slices and serve.