Preheat your oven to 375°F and lightly coat an 8-by-8-inch baking dish with cooking spray.
In a large bowl, stir together the flour, sugar, cocoa powder, baking powder, and salt until well combined.
In a separate glass measuring cup, combine the milk, lightly beaten egg, canola oil, and vanilla extract. Gradually pour this mixture into the well in the center of the dry ingredients, stirring until well combined. Stir in the toasted pecan halves.
Spoon the batter evenly into the prepared pan.
In a separate bowl, dissolve the brown sugar into the hot strong coffee.
Pour this mixture over the batter in the pan.
Bake the cake until a toothpick inserted in the center comes out clean, which should take around 25 minutes.
Let the cake stand for about 10 minutes before serving it hot or warm.