Preheat oven to 350°F. Grease a 9x13 inch baking pan and set aside.
In a large bowl, combine cake mix, eggs, oil, peach nectar, and vanilla. Beat on medium speed for 2 minutes until smooth.
Gently fold in diced peaches. Spread batter evenly into prepared pan.
Bake for 40-45 minutes until toothpick inserted in center comes out clean. Cool completely.
For frosting, combine brown sugar, cream, and butter in saucepan over medium heat. Bring to boil, stirring constantly for 1 minute.
Remove from heat. Whisk in vanilla and salt. Cool to room temperature, then beat until fluffy.
Spread brown sugar frosting over cooled cake. Serve at room temperature.