Add 3 Tablespoons butter and ¼ cup brown sugar to each of two 9 inch round baking pans.
Place pans in the oven until butter melts, then remove and stir sugar and butter together.
Arrange the pear slices in a circular pattern on top of the sugar butter mixture, with the bottom end of the pear on the outside of the pan. Pears will overlap. Set aside.
To Make The Cake
In a small bowl or measuring cup, mix boiling water and baking soda together. Set aside.
In a medium bowl, whisk together flour, gingerbread spice, and baking powder. Set aside.
Using a stand mixer and bowl**, add ½ cup butter, ⅔ cup brown sugar, and mix on medium until fluffy, about 3-5 minutes.
Add vanilla, then one egg at a time. Beat after each egg until well combined. Add molasses and salt, and mix until well combined.
Reduce to low speed and slowly add flour mixture until combined, scraping the bowl.
Keep mixer on low speed and slowly add water and baking soda mixture. Mix well.
Distribute batter evenly and carefully over the pears in each pan. Spread if needed.
Bake for 30 minutes, or until a or until a toothpick comes out clean.
Cool for about 5 minutes. Run a knife around cake to release from the pan. Place a plate or platter upside down on top of each pan. Use oven mitts to hold the plate and pan together, then flip over. Gently lift pan to release the cake.
Serve warm, or room temperature with ice cream or whipped cream if desired.
*Bartlett pears or any variety will work**A hand mixer can also be used with a large mixing bowl.
Use room temperature butter and eggs, as well as fresh baking powder and baking soda for best results.
Refrigerate cake, or store at room temperature, in a covered container for about 3 to 4 days. Freeze cooled cake wrapped in plastic, and then in a zippered bag or with foil, for up to 4 weeks.
Thaw frozen cake before slicing and serve chilled, or reheat covered with foil, in the oven or the microwave.