In the mixing bowl, add the butter and sugar and beat on medium speed with the stand mixer for 5 minutes, scraping down the sides at least once. Add the eggs one at a time, and beat on low speed until thoroughly combined and scrape the sides of the bowl after each addition. Add the vanilla and salt and beat to combine. Add a third of the flour, beating on low speed until just combined and scraping the sides of the bowl after each addition. Then beat at medium speed for 30 more seconds.