Step 1

Preheat oven to 375°F. Brush a 2-quart baking dish with unsalted butter. In a large bowl, toss together apples, granulated sugar, 2 tablespoons flour, lemon juice, cinnamon, and 1/4 teaspoon salt; transfer to prepared dish.

Step 2

In a bowl with an electric mixer, beat butter with brown sugar until fluffy. Mix in 1 cup flour and 1/2 teaspoon salt until large pieces form. Scatter over filling. Bake until center is bubbling, about 1 hour; if top darkens, tent with foil. Let cool 20 minutes; serve with ice cream.