Preheat oven to 350 degrees. Spray a 9" round or 9x9 baking dish with nonstick baking spray.
Add your butter and sugars to a bowl and mix for 3 minutes until light and fluffy.
Mix in the eggs and vanilla. Add the flour, arrowroot, baking soda, and salt and mix until just combined. Do not over mix.
Fold in the peanut butter or sunflower butter cups. Pour batter into prepared pan.
Bake for 30-35 minutes or until a toothpick comes out mostly clean and the top is golden brown.
Allow to cool before cutting. Enjoy!
Notes
Convection Oven vs Regular OvenIn convection ovens, the fan promotes even heat distribution, allowing you to bake at a slightly lower temperature. Reduce the recommended baking temperature by approximately 25°F when using a convection oven compared to a standard oven.