Estonian Egg-White Cake (Munavalgekook)

I stumbled upon this interestingly hard-to-pronounce Estonian cake - Munavalgekook - which is an egg-white cake.  Like the Angel Cake, it only uses egg whites.  Unlike the Angel Cake, it contains butter which makes this cake moist, spongy and soft with a hint of buttery taste.  

Recipe adapted from Nami-Nami

Ingredients:

200g egg whites (about 6), room temperature
1/2 tsp cream of tartar
150g caster sugar
160g plain flour
10g rice flour
1 tsp baking powder
1 tsp vanilla extract
100g butter, melted and slightly cooled

• Sift together plain flour, rice flour and baking powder.  Set aside.
• Whisk egg whites until foamy.  Add in cream of tartar and whisk until soft peaks form. Gradually add in sugar and whisk until stiff peaks form.
• Gently fold in sifted flours.
• Finally add in melted butter and fold gently.
• Pour batter into a buttered and floured bundt pan and bake in a preheated oven at 180 deg C for about 45 mins or until cooked.
• Leave the cake to cool in the pan for about 10 - 15 minutes before turning out onto the wire rack.