Step 1Heat the oven to 375 degrees. Peel the apples if desired, and core and thinly slice them, placing them in a 2-quart ceramic dish. Sprinkle the lemon juice over the apples and set aside.
Step 2In a large bowl, combine the oats, sugar, flour, butter, cinnamon, cardamom, ginger, lemon zest and salt, mixing the ingredients with your hands until fully incorporated. Sprinkle the topping over the apples.
Step 3Bake until the topping is crisp and the juice from the apples is bubbling, about an hour.
Step 4Serve warm with a very large bowl of unsweetened whipped cream.