In a bowl, rub the flour and margarine until you have a breadcrumb mixture. Add in the sweetener and milk until a dough forms.
Press into a greased and lined loaf tin and push down evenly over the base. Spread over the black cherry filling to cover.
Mix together all of the topping ingredients until a batter forms, then spread over the cherry mixture. Bake at 180°C for 30-40 minutes (cover halfway through) until golden and a skewer comes out clean. Leave to cool.
