Peel, core, and slice the apples. Drizzle lemon juice over the apple slices and set aside.
In a medium skillet, melt the butter over medium heat. Add the apple slices and cook until tender, about 5-7 minutes.
Add the brown sugar, cinnamon, and pinch of allspice. Stir until brown sugar is melted and cook for 2 minutes or until the mixture thickens. Remove from heat.
Toast the bread and spread peanut butter evenly on the slices. Top the peanut butter toast with the skillet cinnamon apples. Garnish with candied walnuts or pecans, if using. Serve immediately.