Banana walnut cake

I had bookmarked this recipe from Grace's Kitchen Corner long time ago, but somehow I totally forgot about it until 2 days ago, when I re-found it while browsing through the recipes that I have in the to-do list.
Well, I love bananas and I love walnuts, so puting them together in a cake sounded like a great idea to me and I already had some bananas and walnuts at home, so I inmediately decided to do it ^^
I only did a few changes because I didn't want to go to the store just to buy some baking soda and butter so I used salted butter and more baking powder, but nevertheless the cake was (please note the use of the word "was" XD) still moist and delicious.
So, the recipe I used is as follows:

Ingredients:        

60g salted butter (at room temperature)
3/4 teaspoon baking powder
80g low fat natural yoghurt
1 large egg
120g all-purpose flour
80g sugar
100g mashed banana
Toasted walnuts (chopped)

Method:

1. Preheat oven to 180ºC.
2. Butter a small (about 17x8x6cm) loaf pan.
3. Cream butter and sugar (add the sugar little by little) until light and pale in color.
4. Mix in the egg and then the baking powder until well combined.
5. Add in the mashed banana and mix until combine (not mix too much).
6. Add 1/3 of the flour, mix well and then add the rest of the flour.
7. Mix in the yogurt until well combined and then fold in the chopped walnuts.
8. Spoon the batter into the prepared loaf pan and bake until a skewer inserted in the center comes out clean, about 50-60 minutes
9. Let it cool completely in the loaf pan on a rack before unmoulding.