Preheat the oven to 180C/170C Fan/Gas 5. Line an 8" square tin.
In a large bowl, or the bowl of a stand mixer, combine the butter and sugar on medium/high for about 3-5 minutes, until fully "creamed".
Add in the eggs and lemon zest and beat again.
Fold in the flour, gently. Then add the orange juice (milk will work too), and fold to loosen it all up to make a smooth batter. Pour this into the lined tin. Bake for 20-25 minutes until a skewer inserted comes out clean.
Make the drizzle by combining the lemon, orange juice and sugar in a bowl. Poke some holes in the cake using a knife/skewer. Pour the drizzle over the cake.
Optional: Once cooled, make the glaze by combining the icing sugar, colour and orange juice in a small bowl and drizzle over. Slice and serve!