Apple streusel cake

This is a recipe from my grandmother that I just slightly changed. It works equally well with other fruit like rhubarb or cherries.

APPLE STREUSEL CAKE

Ingredients:
150ml Sunflower oil
125g Caster sugar
1 Pinch of salt
2-3 Eggs
200g Plain Flour
2 Tsp Baking powder
1 Lemon (juice and zest)
1 Tsp Ground cardamon
3-4 Apples
40g Unsalted butter
50g Flour
50g Sugar
1 Tbsp Vanilla sugar

Heat oven to 180°C/Gas 4. In a bowl mix oil, caster sugar and salt. Add the eggs and whisk together until fully blended and smooth. Sift flour with baking powder into the mixture. Add lemon juice and zest and the ground cardamon. Pour the mixture into a greased baking tin. Slice the apple and spread over the mixture. For the streusel mix butter, sugar, vanilla sugar and flour and sprinkle evenly over apples. Bake in the oven for 45 min.