Peel and slice the tart apples. Ensure the apple slices are not too large to ensure even cooking without excessive browning.
Heat oven to 375º. Grease the bottom and sides of a 9 x 13” pan.
Spread the sliced apples evenly in the greased pan.
In a mixing bowl, combine brown sugar, all-purpose flour, oats, ground cinnamon, and ground nutmeg. Mix until well blended as this will be your topping.
Incorporate the softened Kate's Butter into the dry mixture. You can use your hands for this step to achieve a crumbly texture. For an extra crispy apple crisp, feel free to double the amount of topping.
Sprinkle the topping evenly over the sliced apples in the pan.
Bake for about 35 minutes at 375º or until the topping turns a golden brown, and the apples are tender when pierced with a fork.
Remove from oven and let rest for 5 minutes.
Enjoy your apple crisp warm and serve with a scoop of vanilla ice cream, if desired.