- 3 large firm, crisp-sweet apples, such as Pink Lady or Honeycrisp (do not use a soft variety like Cortland or McIntosh—they will not hold their shape)
- 3 tablespoons unsalted butter, divided
- 3 1/2 tablespoons brown sugar, divided
- 1 1/2 teaspoons ground cinnamon, divided
- 3 tablespoons old-fashioned rolled oats
- 2 teaspoons white whole wheat flour (or all purpose flour)
- 1/4 teaspoon kosher salt
- Low-fat vanilla ice cream or vanilla frozen yogurt, for serving
- Place a rack in the center of your oven and preheat the oven to 400 degrees F. Coat the inside of a 9×13-inch or similar glass or ceramic baking dish with nonstick spray and set aside.
- Peel the apples, then cut them in half from top to bottom. With a melon baller or small spoon, remove the core. Turn the apples cut-side down on a cutting board. Starting at the outermost edges, cut 1/4-inch slices most (but not all) of the way through each apple. Place apple halves, cut sides down, in the prepared baking dish.
- Melt 1 1/2 tablespoons butter in a small saucepan or microwave-safe bowl. Stir in 1 1/2 tablespoons brown sugar and 1/2 teaspoon cinnamon. Brush the mixture evenly over each apple.
- Cover the pan with foil. Bake for 20 minutes, then remove the pan from oven, uncover, and let cool 10 minutes. Increase the oven temperature to 425 degrees F.
- While the apples cool, make the streusel topping: Melt the remaining 1 1/2 tablespoons butter in the same bowl or saucepan used previously. Stir in the remaining 2 tablespoons brown sugar, 1 teaspoon cinnamon, oats, flour, and salt. Carefully fan open the apple halves and with a fork or spoon. Work the some streusel between the slices and sprinkle some over the top.
- Return to the pan to the oven and bake uncovered at 425 degrees F until the apples are tender and the topping is brown, about 10 to 15 additional minutes. Let cool for a few minutes, then serve warm with ice cream.