Preheat the oven to 170°C. Grease and line a loaf tin.
Mash the bananas in a small bowl. Add the cinnamon, then the oil and eggs. Mix in the oats, sugar and oat milk. Let it rest for 5 minutes.
Mix in the flour and ground nuts or almonds until you get a batter, then fold in the sultanas.
Tip the mixture into the tin, allowing to spread out evenly.
Bake for 50-60 minutes in the middle of the oven, until an inserted skewer comes out clean.
When the banana cake is ready, take it out of the oven and let it cool for 5 minutes in the tin, then transfer it to a wire rack.
Let it cool completely, then slice.