For the brownies: Preheat the oven to 325 degrees F. Line one 9- by 3-inch cake pan with parchment paper and lightly coat with oil; set aside.
Whisk together the flour, cocoa powder, baking powder, baking soda and salt in a medium bowl. Add the oil, agave nectar and applesauce directly into the dry ingredients. Stir until the batter is smooth.
Pour the batter into the prepared pan. Bake on the center rack until a toothpick inserted in the center comes out clean, 20 minutes.
For the pizza: Beat the cream cheese, sugar and pineapple together in a bowl with a spatula. Spread the mixture over the cooled brownie crust. Arrange the strawberry and banana slices over the cream cheese mixture. Sprinkle with the chopped walnuts. Freeze for at least 30 minutes. To serve, slice as you would a pizza, and enjoy!
Nutrition information per serving: 580 calories; 28 g fat