Steps

Directions
Preheat the oven to 350°F. To prepare the pears, cut the pears into 1/4-inch slices. Melt butter in a 10-inch cast iron skillet over medium heat. Add the brown sugar and salt and cook until melted, stirring occasionally. Remove from the heat, add the vanilla and combine.
Decoratively place the pear slices on the caramel, overlapping them as a circle of pears in the center.
To make the cake, add the flour, cocoa powder, sugar, baking powder, baking soda and salt to a large mixing bowl and whisk to combine.
Combine the milk, oil, egg, yolk and vanilla in large glass measuring cup and whisk to combine. Pour over the dry ingredients and fold until smooth.
Add espresso powder and boiling water to the measuring cup, whisk until incorporated and pour the mixture into the mixing bowl, whisking a final time.
Pour the batter over the pears in the prepared pan and bake for 25 to 30 minutes, rotating at the halfway point. The cake is ready when a toothpick inserted and comes out with a moist crumb.
Immediately run a paring knife around the edge of the skillet. Let sit for 5 minutes, then carefully invert the cake onto a serving platter.
Let cool until the caramel sets a bit, about 20 minutes, or cool to room temperature. Serve with vanilla ice cream or whipped cream.