1. Position a rack in the center of the oven and preheat the oven to 325°F. Grease the bottom and sides of a 9 × 3-inch round cake pan or springform pan. Dust the pan with flour.

2. Sift together the flour, cocoa powder, baking powder, baking soda, and cinnamon into a medium bowl. Whisk to combine, and set aside.

3. In the bowl of an electric mixer, using the paddle attachment, beat the butter at medium-high speed until creamy, about 1 minute. Gradually add the brown sugar and beat at high speed until very light and creamy, about 3 minutes. Reduce the speed to medium-low and add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl with a rubber spatula as necessary. Beat in the vanilla extract. Reduce the speed to low and add the dry ingredients in three additions, alternating with the stout in two additions and mixing just until blended. Add the pecans and mix just until combined. Remove the bowl from the mixer stand and stir a few times with the rubber spatula to make sure the batter is evenly blended. Scrape the batter into the prepared pan and smooth the top.

4. Bake the cake for 70 to 75 minutes, until a cake tester inserted into the center comes out clean. Cool the cake in the pan on a wire rack for 20 minutes.

5. Invert the cake onto the rack and cool completely.

6. Just before serving, dust the top of the cake lightly with confectioner’s sugar.