Preheat oven to 350°F. Line one 8x8 or 7x9 baking pan with parchment or lightly oil and set aside.
Whisk together gfJules Flour, sugar, baking soda and baking powder in a bowl and set aside.
Add butter, cocoa (or Chocolate Protein Powder), water and lemon juice to a sauce pan and heat to medium on a stove top, stirring constantly. Once boiling, continue stirring for 20-30 seconds, then remove from heat. Whisk in aquafaba (or egg) and vanilla.
Pour chocolate mixture into flour bowl and stir until combined. Quickly transfer to prepared baking pan, smooth top and place in oven to bake for 13-14 minutes.
Cake is done when it springs back to the touch and a toothpick inserted into the center comes back clean, but not wet.
With 5 minutes left of bake time, toast pecans on a baking sheet, if using.
Prepare frosting by adding butter, milk, cocoa (or Chocolate Protein Powder) and powdered sugar to saucepan over low-medium heat, whisking to integrate the sugar and cocoa. Once totally mixed and the butter is melted, remove from heat -- do not bring to a boil. Add vanilla extract.
When cake is done, remove to cool on a wire rack and pour frosting over top cake. It will set quickly, so if adding pecans, sprinkle on immediately after pouring.