Start with your ingredients at room temperature. Preheat the oven to 350°F and grease a 9" springform pan or a cake pan that's at least 2½ inches deep.
In a small mixing bowl, combine the melted butter and brown sugar; mix well and pour the mixture into the prepared pan. Tilt the pan a little from side to side to help the mixture spread all the way to the edge.
Arrange the sliced pears side-by-side over this brown sugar mixture, making sure that they cover the entire bottom of the pan. Set aside.
In a large mixing bowl, combine the dry ingredients and mix well with a whisk until airy and fully combined. Set aside.
In the bowl of your stand mixer equipped with the paddle attachment, beat the the butter and brown sugar on medium-high speed until light and fluffy, about 3 minutes.
Add the eggs and beat again until pale and airy.
Incorporate the apple sauce and molasses, mix until well combined, and then add the dry ingredients and mix on low speed until just incorporated, no more.
Pour over the pears and spread all the way to the edge.
Place a piece of aluminium foil under or around your pan to catch any eventual leakage and bake for 60 minutes or until a toothpick inserted in the center comes out clean.
Let the cake cool for 10 to 15 minutes or until it's cool enough to be handled safely then flip it onto a rimmed cake plate.
Serve warm, garnished with vanilla ice cream, chopped nuts and a drizzle of honey or caramel sauce, if desired.