Pineapple and Lime Cake

I realise that most cakes i make lately are quite plain but right now with trying to cut down,other desserts don't really appeal.The great thing with this cake is that you can substitute the sour cream for plain yogurt and it's quite delicious and anybody can have a slice or 2.
Recipe is by Bill Granger and it appeared a few months ago in his weekly column in the Sydney Morning Herald which he has recently had to withdraw from.

Topping
1 cup firmly packed brown sugar
1/4 cup plain flour
75g unsalted butter,cold

Cake
2 cups plain flour,sifted
2 tsp baking powder
1/4 tsp salt
125g unsalted butter,softened
1 cup caster sugar
zest if 1 lime
3 eggs,lightly beaten
1 cup sour cream or plain yogurt
1 1/2 cups diced pineapple

Preheat oven to 180c.
To make the topping place brown sugar and flour in a bowl, add butter and rub in with fingertips until the mixture resembles coarse breadcrumbs.

To make the cake sift the flour,baking powder and salt into a mixing bowl.Place butter,sugar and lime zest in a second bowl and cream together.Add the eggs and milk
Add the dry ingredients to the egg mixture,alternating with sour cream and mixing well after each addition.
Pour the cake batter into a lined 20 cm round or square cake tin.Sprinkle over the pineapple and then the topping mixture.
Bake the cake for 40 to 50 minutes or until a skewer comes out clean.Leave to cool in the tin for 10 minutes,then turn out onto a wire rack,topping side up.Serve warm or at room temperature with double cream or ice cream.