Pre-heat oven to 350f degrees and grease/line an 8x8 inch baking dish.
Mix first 4 ingredients together well in a stand or hand mixer.
Separately, mix all dry ingredients (flour, cacao, cinnamon, salt, baking soda) with a whisk in another bowl.
Add the dry mixed ingredients to the wet while continuously mixing.
Then add in the sweetener of choice, followed by milk. If you'd like to add chocolate chips, chopped nuts or anything else, add this in with a spatula to combine. Taste batter to make sure it's to your liking (or add more sweetener if you need).
Pour batter into your greased/lined pan and top with a little bit of sea salt!
Bake for 25-30 minutes and when it's done, let cool for 15 mins before slicing. Stores well in an air-tight container to stay moist.