Preheat your oven to 180℃ fan/200℃/Gas Mark 6.
Place a baking sheet or baking tray into the oven to warm while it is preheating.
In a large bowl, add your sugar and butter to a bowl and mix using an electric whisk until the mixture is combined and light and fluffy.
Put in your pumpkin, flour, bicarbonate of soda, eggs, cinnamon, nutmeg and lemon zest. Whisk until just combined.
Line a square tin (20cm x 20cm) with baking paper or baking parchment. Pour in your cake mixture and smooth out.
Bake for 30 minutes or until a sharp knife comes out clean.
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