Preheat the oven to 180C/ 160C fan/ Gas mark 4. Grease and line an 18cm round cake tin with baking parchment. Set aside 12 pecans and roughly chop the rest.
In a large bowl, mix together the flour, cinnamon, bicarbonate of soda, xylitol and chopped pecans.
In a separate bowl or jug, beat the eggs and rapeseed oil together. Pour into the flour mixture and stir until combined. Stir through the carrot and sultanas. Spoon into the lined tin, smooth the surface and press whole pecans to form a circle around the edge.
Cook for 1 hour - 1 hour 10 mins until the top feels springy to the touch and a skewer inserted into the cake comes out clean. Check after 50 mins, if the cake is becoming too dark, cover loosely with foil. Cool on a wire rack for 10 minutes, then turn out and allow to cool. Serve slightly warm or cold. This cake keeps for up to five days in a tin. Before serving, drizzle with agave syrup if you have a sweet tooth.