Preheat the oven to 350 degrees F. Line a 9-inch x 5-inch loaf pan with parchment paper. Set aside.
In a large mixing bowl, beat together the sugar, butter, milk, eggs, and vanilla until light and fluffy, about 2 minutes.
In a medium mixing bowl, whisk together the flour, baking powder, and salt. Add the dry ingredients to the wet ingredients and beat until just combined. (Do not overmix! It will make the cake dense.)
Pour the batter into the prepared loaf pan and spread it into an even layer.
Bake for 50-60 minutes or until a toothpick inserted in the center comes out clean. (Start checking for doneness after 45 minutes of baking.) If the cake starts to get too dark on top, loosely cover the pan with foil.
Remove from the oven and let the cake cool in the pan for 20 minutes. Then use the parchment paper to lift the cake from the pan and transfer it to a wire rack to cool for another 30 minutes before serving.
Notes
Store leftovers in plastic wrap or in an airtight container in the fridge for up to 4 days. You can also freeze this cake for up to 3 months. I like to wrap the individual slices in plastic warp, and then put them in a freezer bag. Then I thaw them in the fridge overnight and have just the right amount of cake.