Preheat the oven to 325°F (165°C)
Grease and flour a loaf pan or bundt pan
Cream together 1 cup unsalted butter and 2 cups sugar until light and fluffy
Beat in 4 large eggs one at a time
Mix in 1 teaspoon vanilla extract
In a separate bowl, whisk together 3 cups all-purpose flour, 1/2 teaspoon baking powder, and 1/2 teaspoon salt
Add the dry ingredients to the butter mixture alternately with 1 cup milk or buttermilk
Mix until just combined
Pour the batter into the prepared pan
Smooth the top with a spatula
Bake for 60 to 75 minutes, or until a toothpick inserted in the center comes out clean
Cool in the pan for 10 to 15 minutes
Remove from the pan and cool completely on a wire rack
Slice and serve