For the toffee sauce, mix double cream, 500g milk, sugar, butter and salt in a saucepan. Bring to the boil and reduce by half. Add the remaining milk. Keep the sauce in a warm place.

Preheat the oven to 350°F. Combine the bicarb of soda with 235ml water. Bring to the boil then allow to cool. Sieve together the flour and baking powder. Cream together the butter and sugar, then add the lemon zest and salt. Add the eggs slowly until they are combined. Mix in half the flour then pour in the water and bicarbonate of soda and mix until the liquid is absorbed. Fold in the rest of the flour. Pour the mixture into a lined baking tray, approximately 10" square, and bake for 25 minutes. Cool then cut into portions. Reduce the oven to 260°F, warm the cakes for 5 minutes then generously spoon over toffee sauce. Put the cakes back into the oven for a further 5 minutes then baste with more hot toffee sauce to serve. There should be spare sauce - serve it in a jug.

For the apple purée, chop the apples. Combine with the butter, sugar and vitamin C powder. Cook in a saucepan until tender, about 20 minutes. Blend into a smooth puree and serve alongside the cake