Pour batter into greased cake pan and place in oven. Bake for 20 minutes, or until toothpick inserted in center comes out clean. Remove from oven and let cool 10 minutes.
While cake cools, prepare frosting. Combine butter, heavy cream and brown sugar in a medium saucepan over medium-high heat. Whisk everything together and bring to a boil, then stir in vanilla extract and remove from heat.
Stir in powdered sugar and whisk until smooth, then pour frosting over cooling cake. Optional: fold pecans into frosting before pouring, or sprinkle over the top.
