In a 12-inch cast-iron skillet, melt butter over medium heat. Remove from heat; stir in brown sugar, ginger, and cornstarch until mixture is the consistency of wet sand. Arrange pears in concentric circles in sugar mixture, overlapping fruit as needed, to fully cover bottom of skillet.
In a large bowl, whisk together cake mix, ½ cup water, oil, and eggs until thick, smooth, and well combined. Gently spread batter onto fruit.
Bake until top is dry and a wooden pick inserted in center comes out clean, 30 to 35 minutes. Let cool in pan on a wire rack for 5 minutes. Carefully invert cake onto a plate; serve warm.
Notes
KITCHEN TIP-Try to slice your pears 3/16 inch thick so they’ll stay on top of the batter as the cake bakes. Batter tends to bake up and around thicker slices of fruit, but your cake will be delicious no matter what.
Recipe by Southern Cast Iron at https://southerncastiron.com/gingered-pear-chocolate-upside-cake/