Preheat the oven to 350 degrees F (175 degrees C). Lightly grease an 8-inch square pan with coconut oil.

Whisk arrowroot, cocoa powder, and cinnamon together in a bowl.

Combine chocolate morsels and butter in a large microwave-safe bowl. Melt in the microwave in 30-second increments, stirring after each, until melted and smooth, about 2 minutes.

Stir palm sugar and vanilla extract into the bowl with the melted chocolate. Blend in eggs 1 at a time until combined. Add arrowroot mixture and stir vigorously until mixture is smooth and begins to pull away from sides of the bowl. Blend pecans into batter.

Pour batter into the prepared pan and smooth the top with a spatula.

Bake in the preheated oven until a toothpick inserted in the middle comes out with a few moist crumbs, 30 to 35 minutes. Allow to cool.

Store in the refrigerator or freezer.