Heat oven to 180C/fan 160C/gas 4. Grease and line a 30 x 20cm baking or small roasting tin with baking parchment. Put the gluten free flour, sugar, spice, bicarbonate of soda and salt into a large bowl and stir to combine.
Beat the eggs into the melted lactose free butter, stir in the orange zest and juice, then mix with the dry ingredients till combined.
Stir in the pumpkin. Pour the batter into the tin and bake for 30 mins, or until golden and springy to the touch.
To make the frosting, beat together the lactose free soft cheese, lactose free butter, icing sugar, orange zest and 1 tsp of the juice till smooth and creamy, then set aside in the fridge.
When the cake is done, cool for 5 mins then turn it onto a cooling rack. Prick it all over with a skewer and drizzle with the rest of the orange juice while still warm. Leave to cool completely.
If you like, trim the edges of the cake. Give the frosting a quick beat to loosen, then, using a palette knife, spread over the top of the cake in peaks and swirls.
If you’re making the cake ahead, keep it in the fridge then take out as many pieces as you want 30 mins or so before serving. Will keep, covered, for up to 3 days in the fridge.