A nutrition-packed flourless cake that's just slightly sweet with a healthy, low fat greek yogurt frosting.
Grease and line an 8" cake tin. Preheat the oven to 350 F.
Grind the muesli in a food processor until it is finely ground. You want it in fine griains, slightlt more coarse than flour. so keep processing in short bursts until it reaches that consistency. Put the butter and sugar into a large bowl and beat it until it is light and fluffy. Add in the eggs one by one, beating well after each addition.
Stir in the ground muesli and baking powder, then add 2 tbsp lemon juice. Mix well and pour the mixture into the prepared tin, then level the top. Bake on the middle shelf of the oven for 45-60 minutes. Check the cake after 45 minutes - it is ready when a skewer comes out clean.
While the cake is baking, combine ⅓ cup lemon juice and 6 tablespoons of brown sugar in a small saucepan. Stir to combine and then heat over low heat until the sugar has dissolved. When the cake is done, remove it from the oven and prick it all over with a skewer, then pour the lemon syrup over the hot cake. It seems like a lot of syrup, but it will all soak in.
Leave the cake to cool in the tin, then remove it and wrap it in foil or put it in an airtight tin. Served with lightly sweetened Oikos Greek Yogurt.