Preheat your oven to 350 F (176 C).
Melt your butter over medium heat.
Add sugar, melted chocolate, and vanilla extract to the pan and whisk together well.
Let your mixture cool for a 5-10 minutes. Add your eggs one at a time, whisking well to incorporate. If your mixture is too hot, it could scramble your eggs, so wait a few more minutes to add the eggs if needed!
Measure out your dry ingredients (almond flour, cocoa powder, and salt).
Sift into the wet ingredients and fold together until incorporated.
Prepare your baking pan (it can be either square or round - we used a 9 inch round cake tin for this recipe) by buttering the sides and bottom and lining with parchment paper.
Pour in your mixture and bake in the oven for about 30 minutes.
The final consistency is similar to a brownie, so if you test the cake with a knife a few crumbs should still stick to the knife.