Combine oat milk and apple cider vinegar in a glass. Let it sit for 10 minutes.
Preheat the oven to 175 degrees Celsius.
Line or grease a 20 cm spring form.
Combine mashed banana, apple sauce and yogurt in a bowl and whisk until you have a smooth mixture.
Add the sweetener, oat milk, eggs, vanilla extract and coconut oil and incorporate into the mixture.
Combine the rest of the ingredients (except for the raspberries) in a separate bowl.
Add dry ingredients to the wet and stir together until you have a smooth batter. Do not mix for too long.
Gently fold in about 3/4 of the raspberries into the batter.
Pour the batter into the prepared spring form.
Add the ingredients for the crumble to a small bowl. Stir to combine until you have a crumbly dough. If needed add some more coconut oil or apple sauce.
Top the cake with the rest of the raspberries and crumble. Press down gently.
Bake in the middle of the oven for 35-40 minutes, until a toothpick comes out clean.
Take out from the oven and let it cool completely before removing it from the spring form and slicing it.
Top with icing sugar (optional).