Gather butter, eggs, sugar, coffee, walnuts, and flour.
Combine the wet ingredients with the flour, sugar, and baking powder.
Gently fold in chopped walnuts for crunch and texture.
For even baking, preheat the oven to 180°C (350°F).
Pour the batter into a baking pan that has been lined and oiled.
A toothpick should come out clean after baking for 30 to 35 minutes.
Once cool, cover with coffee frosting and add walnut halves as a garnish.