Preheat oven to 375.
Butter an 8-inch cast-iron skillet and set aside.
In a small bowl, combine sliced pears and lemon juice; toss together and set aside.
In a separate bowl, whisk together flour, salt, and baking powder; set aside.
In your mixer's bowl, cream together butter and sugar until light and fluffy.
Add eggs and continue to beat until mixed.
Mix in vanilla; beat until thoroughly combined.
Set your mixer on the lowest setting and slowly add in the flour mixture; mix until thoroughly combined.
Add half of the pear slices to the cake batter and fold them in.
Pour batter into prepared skillet.
Using an offset spatula, spread the batter evenly and smooth it out.
Add the rest of the pear slices on top and push them into the batter.
Bake for 30 to 35 minutes, or until a toothpick inserted in the center of the cake comes out clean.