Preheat oven to 350°F.
Remove stems by cutting a 1-inch-wide hole out of the top of each apple. Cut into the hole to remove and scoop out the core and seeds.
Rinse lemon and cut in half. In a small bowl, squeeze the juice from each half. Discard seeds.
In a second small bowl, mix walnuts, raisins, and brown sugar.
Stuff the center of each apple with 1 heaping Tablespoon of the walnut mixture. Sprinkle a pinch of cinnamon over the top of each apple.
Place stuffed apples upright in the baking dish. Pour the lemon juice around them. Bake for 35–40 minutes, or until the skin is wrinkly. Spoon some of the pan juice over the apples about halfway through cooking time to keep the apples moist.