Melt butter in 9” sauté pan. Add sugar.
Peel and core pears, cut in half. Place pears cut-side down in pan. Over low heat, cook pears for 12 minutes.
Carefully invert pears and cook additional 10 to 12 minutes until al dente and sugar just begins to caramelize.
Remove from heat.
Cut piecrust to fit over pears, allowing a ½” margin all around. (I use a readymade piecrust.) Egg wash edge of dough and roll up to form an even rim around circumference of disc. Crimp with a fork to seal the seam.
Invert pastry onto cooled apples, fluted side facing down, and tuck edge of dough down and under pears. Press dough lightly on top so it adheres to pears.
Egg wash piecrust; pierce with fork.
Bake at 400 degrees until crust is lightly browned (about 20 minutes). Let cool on rack a few minutes. You may need to run a knife around the edge in case the crust has stuck to the skillet. Carefully invert tart onto serving tray. Serve unadorned or with vanilla bean ice cream.