Sieve the flour,baking powder and salt and keep aside
Mash the bananas well and whisk in the sugar
Add spinach puree,vanilla essence and lemon juice and mix well
Fold in the flour softly till no lumps
Pour the batter in cupcake liners or small cake tin pans
Bake in preheated oven at 180 degree Celsius for 18-20 mins
Remove and cool completely
For the frosting whisk the butter at room temperature for 1-2 mins till soft and pale in colour
Add icing sugar in batches till all is incorporated
Add yellow food colour and butterscotch essence and milk ,if required
Put the frosting in a piping bag and frost the cupcakes
Sprinkle some chopped pistachios and serve