Place the sugar for the salted caramel in a pot and place over very low heat
Pre-heat the oven to 150 °C combi mode and place the nuts on a small baking tray and toast for 4-5 minutes until golden, remove and set aside
In the bowl of a stand mixer place egg yolk, limejuice and 150gm of caster sugar, mix on medium speed until well combined. Add the flour and mix again for 1 minute on medium speed. While the mixer is still running pour in the oil in a steady stream until the mixture is smooth.
Remove the mixture from the bowl of the mixer and place it into a large mixing bowl and set aside. Clean the bowl of the mixer and whisk then pour in the egg whites to the mixing bowl, attach the whisk and beat on high seed until the whites begin to form soft peaks. Add half of the remaining sugar and beat for another 30 seconds then add the rest of the sugar and beat for another minute
Add 1/3 of the egg whites to the olive oil mix and mix through with a spatula. Add another 1/3 and fold through gently until well combined, repeat with the remaining mixture
Line the cake tin with baking paper and pour the cake mix in and cover the top with foil
Place into a pre-heated oven combi setting 160 °C for 23 minutes
Once the sugar on the stove has melted turn up the heat and cook until a deep copper colour is achieved, remove from the heat and carefully drop in the butter, shake or stir the pan until the butter is combined and melted through.
Add the cream and stir through until melted, season well with salt and taste. Add additional salt if required and pour into a bowl and set aside
Place the nuts into a mortar and pestle and crush slightly leaving a few large pieces, pour the crushed nuts into a bowl and add the cinnamon and icing sugar and stir through and set aside
Once baked remove the cake from the oven and place on a cake rack, remove the foil from the cake and the outer ring and cool at room temperature