1. Preheat the oven to 180°C, fan oven 160°C, Gas Mark 4. Grease and line a round 20cm (8 inch) loose-based cake tin.
2. Whizz the muesli in a food processor until finely ground. Think of the texture of ground almonds, so keep processing in short bursts until it reaches that consistency.
3. Cream the butter and sugar into a large bowl until light and fluffy. Gradually add the eggs, beating well between each addition. Stir in the ground muesli and baking powder, and then add the grated zest from 1 lemon and the juice of half a lemon. Get your muscles going and mix well, then spoon into the prepared tin, levelling the surface.
4. Bake on the middle shelf of the oven for 45-50 minutes. Check the lemon muesli cake after 45 minutes – you’ll know it’s ready when a skewer comes out clean.
5. While the lemon cake is baking, grate the rind from 2 lemons and extract the juice from the remaining 3 1/2 lemons. Place the lemon rind and juice in a small saucepan with the 6 tablespoons of sugar. Stir to combine and then heat over low heat until the sugar has dissolved into an aromatic lemon syrup. Mmmmmm.
6. When the lemon muesli cake is done, remove it from the oven and prick it all over with a skewer, then spoon 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 serve yourself a slice, you’ve earned it. You can wrap the rest in foil or put it in an airtight tin to save for later.
You can serve the muesli cake straight out of the tin, but it is also lovely warmed up.
Try serving this lemon cake recipe with a dollop of crème fraiche or thick Greek yogurt.