Step 1: Prepare the Peaches: Gently toss the sliced peaches in a bowl. If the peaches are not very sweet, sprinkle with 2 tablespoons of the granulated sugar to enhance their natural flavor.
Step 2: Combine Cake Mix and Wet Ingredients: In a separate bowl, whisk together the white cake mix, melted butter, milk, and vanilla extract (if using) until a smooth batter forms. Avoid overmixing; a few lumps are acceptable.
Step 3: Assemble the Dessert: Pour the cake batter into a greased 9x13 inch baking dish. Evenly distribute the sliced peaches over the batter.
Step 4: Add Optional Topping: If desired, sprinkle the remaining 2 tablespoons of granulated sugar evenly over the peaches. This creates a slightly caramelized top as it bakes.
Step 5: Bake to Golden Perfection: Bake in a preheated oven at 350F (175C) for 30-35 minutes, or until the cake is golden brown and a toothpick inserted into the center comes out clean.
Step 6: Cool and Serve: Let the cake cool for at least 15 minutes before serving. Dust with powdered sugar, if desired. Serve warm, plain or with a scoop of vanilla ice cream.
Optional Tips and Substitutions:
For a richer flavor, use brown butter instead of melted butter. Simply melt the butter in a saucepan over medium heat until it turns golden brown and has a nutty aroma, then let it cool slightly before using.
Substitute canned peaches (drained) if fresh peaches are not available.
Add a sprinkle of cinnamon or nutmeg to the cake batter for added warmth.
For a crumble topping, mix 1/2 cup flour, 1/4 cup sugar, and 1/4 cup cold butter (cut into small pieces) until crumbly. Sprinkle over the peaches before baking.