Prepare your baking pan by either spraying with baking spray or greasing & flouring and set aside. Combine flour, baking powder and salt and set aside. Combine buttermilk and vanilla extract and set aside.
To a mixing bowl, add butter and sugar. Mix on high speed until light and fluffy. Visually, the sugar and butter will go from yellow to very pale yellow/white and you will not feel as much of the sugar in the butter. About 7-10 mins.
Scrape down sides of the bowl, being sure to get the bottom, and add eggs one at a time on medium speed until they are all combined.
On low speed, alternate adding flour blend and buttermilk mixture, 1/3 at a time. After final addition of buttermilk and flour, mix until just combined. Some streaks of flour may remain. Fold the mixture together by hand, being sure to scrape the bottom and sides once more to ensure everything is thoroughly combined without over mixing.
Add evenly to your baking pan and tap firmly on the counter for about 1 minute to ensure all air bubbles are removed.
Place on the center rack of a cold oven, and set oven to 325. Bake for 45 mins to 1 hour, or until a knife inserted into the middle comes out mostly clean with just a few streaks on the knife (NOT batter, but streaks of moisture.). Cool COMPLETELY in pan.
Make glaze by combining all of the ingredients in a bowl or measuring cup with a pouring spout. Taste and adjust for additional salt and vanilla flavor. Pour over cake and allow glaze to run down the sides. Let sit for 10-15 mins to set. Cut and enjoy!
*Cake can set on counter in cake keeper for up to 5 days and will stay moist and soft.