Zanny's rhubarb cake

Ingredients

• 300g dark brown sugar
• 65g butter
• 2 eggs
• 300g plain flour
• 1 teaspoon bicarbonate of soda
• 1 teaspoon salt
• 1 lemon's rind grated
• 2 teaspoons cinnamon
• 1 teaspoon vanilla
• 600g rhubarb chopped
• 250g light sour cream
• 80g brown sugar
• 1 teaspoon cinnamon