Heat oven to 350°F.
Grease an 9” cake pan and cut a parchment paper circle to fit the bottom.
In a bowl, beat together the cake mix, eggs, milk and oil.
Drain all cans of peaches (reserving juice) and cut slices in thirds. Add one can of sliced peaches to cake batter; mix well than transfer to the prepared pan.
Bake for 40 minutes then reduce heat to 300°F. Bake an additional 20-25 minutes until cake has set.
Cool 10 minutes then invert onto a wire rack.
Pour 2 cups reserved peach juice into a medium saucepan and bring to a boil.
Remove 2 tbs. liquid from saucepan and stir in the cornstarch (mixing corn starch with hot liquid will prevent lumps) Pour back into the peach juice, reduce heat and stir in sugar, salt and butter.
Simmer for 10-15 minutes until juice becomes syrupy; remove from heat and stir in lemon juice and remaining peaches.
Ladle peaches and syrup over slices of cake and serve with a dollop of whipped cream.