Mix oats thoroughly with baking soda. Whisk milk and egg in a separate bowl.
Stir together the milk mix with oats, zest, almonds and sweetener.
Grate two apples and stir them through the oat mixture. Let it stand for 10 minutes. Meanwhile, slice the third apple thinly.
Line a 20x30 cm baking dish with baking paper and arrange half of the apple slices in the bottom. Sprinkle with cinnamon. Smooth the oat mixture on it and arrange the second half of the apple slices on the top, sprinkle with cinnamon again.
Bake in hot oven 200-220 °C for about 40 minutes, until the apples caramelise slightly.
Note: if desired, add 50 g raisins or other chopped dried fruit to the oat mixture.
There are 137 calories in 1 serving of Apple & Oats Slice.