Preheat the oven to 350°F. Prepare a 9x13 baking dish. (I used GOOP, click the recipe in the Notes)
In a large bowl, beat the butter and brown sugar together with a hand-held mixer until smooth.
Add the eggs one at a time, incorporating them into the butter mixture fully. Scrape the sides of the bowl if needed.
Pour in the buttermilk and vanilla extract. Mix until combined. (Make sure there are no lumps)
Add the flour, baking soda, and salt to the wet ingredients. Stir by hand with a spatula until ingredients are incorporated.
Pour the batter into the prepared pan.
Bake the cake for 30 minutes. Ten minutes before the cake is done, prepare the topping.
PECAN GLAZE
Stir the butter and brown sugar together in a small bowl. (I used a 2 cup measuring cup) Add the buttermilk, chopped pecans, and salt. You should easily be able to pour the glaze.
When you take the cake out of the oven, immediately pour the pecan glaze all over the cake. Then return it to the oven for 10 more minutes.
When the cake is done, the glaze should be bubbling and appear runny and seeping into every nook and cranny of the cake.
Serve warm.
(If you prefer to serve at room temperature, the glaze will have hardened a bit.)