Cut the avocado, remove the stone and scoop the flesh into a bowl.
Add salt, black pepper and a splash of lemon juice, then mash until mostly smooth.
Stir in the chopped red pepper and set the avocado mixture aside.
In a separate bowl, combine the oats and egg and mix until fully combined.
Heat a little sunflower oil in a non‑stick pan over medium heat.
Divide the oat mixture into two portions and cook each portion like a small pancake, frying on both sides until golden and cooked through.
Place one oat pancake on a plate and spread the avocado mixture over it.
Top with chopped tomato and cucumber, then sprinkle with green onions.
Cover with the second oat pancake to form a stack and serve immediately.