Preheat oven to 375 degrees F. Lightly grease an 8-inch square baking dish.

Arrange apple slices evenly in prepared baking dish.

Sift flour, sugar, cinnamon, and salt in a bowl. Cut in butter using a pastry blender or 2 knives until mixture resembles coarse cornmeal; sprinkle over apples.

Bake in preheated oven until topping is golden, 40 to 45 minutes. Cool slightly before serving. Add your choice of vanilla yogurt as a topping.