Preheat the Oven: Set oven to 350°F (175°C).
Prepare the Pie Batter:
Cream together butter and sugar until light and fluffy.
Beat in eggs one at a time, then stir in vanilla.
Combine cocoa powder, salt, and flour in a separate bowl.
Gradually add dry ingredients to wet ingredients, mixing until just combined.
Pour and Bake:
Lightly grease a 9-inch pie dish.
Pour batter into prepared dish.
Bake for 25-30 minutes, or until set in the center.
Cool and Serve:
Let pie cool in dish for 10-15 minutes.
Serve warm with ice cream or whipped cream, if desired.