For the oatmeal apple sheet cake, peel and core the apples, cut into wedges and sprinkle with lemon juice. Preheat the oven to 180 degrees. Mix the oatmeal with the eggs.
Heat the coconut oil and add to the batter with the speculaas spice. Mix well. Add the raisins and nuts as well. Line a baking sheet with parchment paper, spread the batter on it and smooth it out.
Spread the apple slices on top in a fan shape. Put the sheet cake into the preheated oven and bake for about 50 minutes until done. Dust with the cinnamon-sugar mixture while still warm.
Allow to cool. Then prepare the cake glaze with apple juice according to package directions. Pour everything over the sheet cake and refrigerate for about 2 hours.