1. Preheat the oven to 350°F. In a food processor fitted with the metal blade, process the almonds until finely ground, almost like bread crumbs. In a medium bowl: combine the ground almonds, flour, and baking powder. Stir to blend.

2. With an electric mixer on medium speed or in a food processor fitted with a metal blade, beat the butter until softened. Gradually beat in the sugar and continue to beat the mixture until it is thick and pale in color. Add the eggs, one at a time, and beat until incorporated. Gradually beat in the flour mixture and the orange juice, mixing just to combine. Set aside.

3. To prepare the pears: In a well-seasoned 9-inch cast-iron skillet, melt the butter over medium-high heat. Add the brown sugar, stir to dissolve, and cook until bubbly. Add the pear slices in a single layer. Cook in the syrup for about 2 minutes per side, or until both sides are lightly caramelized. (Use tongs to move them around.) Be careful that the syrup does not become too dark. The pears will exude juice and help to keep the caramel from burning. Remove from heat and let cool for 3 minutes.

4. Pour the batter over the pear mixture and gently spread it around to cover the pears. Bake for 50 to 60 minutes, or until a skewer inserted in the center of the cake comes out clean. Remove from the oven. Let cool in the skillet for 10 minutes, then invert it onto a cake plate. Serve warm or at room temperature.

Advance Preparation:

May be prepared up to 8 hours ahead and kept at room temperature.