Place the oats and boiling water into a medium heatproof bowl and stir. Set aside for 20 minutes.
Meanwhile, cream the butter and sugars in another bowl, until pale and fluffy, approximately 3 minutes.
In a small separate bowl, whisk the eggs and vanilla extract together.
Stir the oats until smooth and add in the eggs, stirring until well combined.
Add in the creamed butter and sugar to the oatmeal mix and stir to combine until smooth.
In a large separate bowl, place the flour, baking soda, ground cinnamon and ground nutmeg and stir together.
Pour in the oatmeal mixture and stir to form your cake batter, until no dry portions remain in the base of your bowl.
Pour into your cake tin and smooth out the top.
Place in the oven and bake until golden and a skewer comes out clean, approximately 45 minutes.