Set oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a large bowl, cream together butter and sugar until light and fluffy. Add eggs one at a time, beating well after each addition.
In a separate bowl, whisk flour, baking powder, and salt. Gradually add to the butter mixture, alternating with milk. Mix in vanilla and toasted pecans.
Divide batter evenly between pans and bake for 25–30 minutes or until a toothpick comes out clean. Let cool completely.
In a saucepan, melt butter and add brown sugar. Stir until dissolved. Slowly whisk in cream and bring to a simmer. Remove from heat and cool slightly. Add powdered sugar, vanilla, and salt. Beat until smooth and fluffy.
Place one layer on a serving plate, spread frosting on top, then add the second layer. Frost the top and sides of the cake. Garnish with extra pecans if desired.
