Preheat oven to 350 degrees and spray an 8x8 or 9x5 inch baking pan with non-stick spray.
Combine the almond flour, cocoa powder, salt, and baking powder in large bowl.
Melt the 4oz. of semisweet chocolate with the 1/2 cup butter in small bowl.
While the chocolate is melting, beat the eggs, vanilla, coffee and sweetener together in a medium-sized bowl.
Slowly pour the melted chocolate into the egg/sweetener mixture and whisk to combine.
Add the chocolate mixture into the almond flour mixture and mix until well combined.
Mix in walnuts.
Bake for about 27-30 minutes.
Be sure that a toothpick comes out clean and dry! (cool completely)