Ingredients:
125 grams of unsalted butter - 1 stick (or 9 tablespoons)
100 grams of dark chocolate - 3.5 oz
300 grams of good quality orange marmalade - try 1 cup, maybe 1 1/4 cups
100 grams of sugar (Nigella uses 150 grams) - 1/2 or 3/4 cupts
a pinch of salt - 1/2 teaspoon of salt
2 large eggs
150 grams of self-rising flour - 1 1/3 cups flour, 2 teaspoons baking powder

Melt the butter slowly in a heavy-bottom saucepan. When it's almost melted, add chocolate pieces, stir and take off the heat. Stir with a wooden spoon, until chocolate has melted.
Add the marmalade, sugar, salt and eggs. Stir thoroughly (it's okay to leave small visible chunks of marmalade in the batter).
Add sifted flour, stir and pour into a buttered and floured 20-22 cm loose bottomed cake tin.
Bake at 180˚C (350 degrees F) oven for 45-50 minutes, until the cake has set (test with a knife or wooden stick).
Leave to cool in the tin for about 10 minutes, then slide onto a plate.

I usually serve it warm-ish, dusted with icing sugar. But it's also delicious on the day after.