Meanwhile, in a medium saucepan, combine the butter, cream, brown sugar, and salt. Bring to a boil over medium-high heat, stirring frequently; cook, stirring constantly, for 2 minutes. Remove from heat; stir in vanilla.
Remove cake from oven, and poke all over with a wooden pick; pour ¾ cup (about 195 grams) butter mixture over top, spreading evenly with a small offset spatula. Let cake cool completely in pan on a wire rack. Transfer remaining butter mixture to a small microwave-safe bowl, cover, and refrigerate.
When ready to serve, using a small offset spatula, gently loosen cake from center and edges of pan. Remove cake from pan, and place, flat side up, on a serving plate.
Heat remaining butter mixture in microwave on high in 10-second intervals, stirring between each, until melted and smooth. Using a large spoon, pour butter mixture over top of cooled cake, smoothing and spreading as needed. Garnish with pecans, if desired.