Preheat your oven to 350°F (175°C). Lightly grease a 9×13-inch baking pan.
In a large bowl, beat eggs, then add cake mix, oil, peach nectar, and food coloring (if using). Mix just until combined—don’t overmix!
Gently fold in chopped peaches. Pour into the prepared pan and smooth out the top.
Bake for 28–32 minutes, or until a toothpick inserted in the center comes out with moist crumbs (not batter). Let cool completely before frosting.
In a saucepan, melt the butter over medium heat. Stir in the brown sugar and heavy cream.
Bring to a rolling boil—bubbling across the entire surface—then boil for exactly 1 minute, stirring constantly. Remove from heat and stir in vanilla.
Let the mixture cool at room temperature until it thickens slightly. Stir occasionally for best results. Put it back on a low heat if necessary.
Pour the frosting over the cake, trying to get it evenly coated. Let the frosting harden at room temperature or in the refrigerator before cutting.
