Cake

8 tablespoons unsalted butter, at room temperature, at least 65°F
2 cups light brown sugar, packed
2 large eggs, at room temperature
2 cups buttermilk, at room temperature
2 teaspoons vanilla extract
2 teaspoons baking soda
1 teaspoon salt
3 cups King Arthur Unbleached All-Purpose Flour

Topping

6 tablespoons butter, melted
1 cup light brown sugar, packed
1/4 cup milk
1/8 teaspoon salt
2/3 to 1 cup diced pecans