Preheat oven to 350F.
Butter a 9x5x3 / 8-cup loaf pan (or 8x8 cake pan) and line it with parchment paper.
Sift together the flour, baking powder, cinnamon, and salt.
Stir in the walnuts and set aside.
Stir the dates into the melted butter, breaking up the dates a bit. In a separate bowl combine the bananas and carrots.
Stir in the date-butter mixture, breaking up any date clumps as you go.
Whisk in the yogurt and the eggs. Add the flour mixture and stir until everything just comes together.
Spoon into the prepared pan.
Bake for about 50 - 60 minutes or until toothpick tests clean in the center of the cake - it'll be less if you are using a standard cake pan.
Remove from oven and let cool.
While the cake is baking whip together the cream cheese and agave nectar. Taste. If you like your frosting sweeter adjust to your liking.
When the cake has completely cooled frost the top of the cake with an offset spatula. Makes one carrot cake.