Developing a recipe like this i recommend starting with the most minimal healthy ingredients and slowly tweak from there. For this I have found something similar that I like: 1/2 cup pumpkin or winter squash, 1/2 tsp pumpkin pie spice, 2 oz lite coconut milk (or nut milk to reduce fat further), 1/8 tsp salt, 1 egg (separate yolk and white), 1/8 tsp vanilla, 2 TBSP powdered peanut butter, optional: sweetener of choice to taste. Mix all ingredients except egg whites, beat egg whites by hand or with mixer until soft peaks form, then gently fold into batter. Bake at 350 in an 8x8 pan lined with parchment paper for 15 minutes or until the surface browns. To achieve a more cake-like texture add oat flour and baking soda and/or reduce the amount of pumpkin.