Heat oven to 350 degrees F. In bowl, mix almonds, flour and baking powder.
With mixer on medium speed, or in food processor, beat butter until smooth and creamy, 2 minutes. Gradually beat in sugar until mixture is thick and pale, 3 minutes. Add eggs, one at a time, beating well after each. On low speed, beat in flour mixture and orange juice just until combined.
In well-seasoned cast-iron skillet (bottom should be 9 inches across), melt butter over medium-high. Add sugar, stirring to dissolve; cook until bubbly, 2 minutes. Add pear slices in single layer; cook in syrup until both sides of pears are lightly caramelized, 2 minutes per side (be careful syrup does not become too dark). Remove skillet from heat; let cool 3 minutes. Pour batter over pears, spreading to cover pears.
Bake in 350 degree F oven 40 to 50 minutes or until skewer inserted in center of cake comes out clean. Remove from oven. Let cool in skillet 10 minutes. Then invert onto cake plate. Serve warm or at room temperature. (Cake can be prepared up to 8 hours ahead and kept at room temperature.) Makes 8 servings.