1. Prep: Preheat oven to 375°F (190°C). Line a 9×13″ baking pan with parchment paper, leaving overhang.
2. Make crust dough: In a food processor (or bowl), combine flour, ½ cup sugar, 1 tsp cinnamon, and salt. Pulse in cold butter until mixture resembles coarse crumbs with pea-sized butter bits.
3. Reserve topping: Set aside 1 cup of the crumb mixture for the top.
4. Press base: Press remaining dough evenly into bottom of pan. Bake 10 minutes to par-bake.
5. Make filling: While crust bakes, toss apples with sugars, flour, cinnamon, lemon juice, and nutmeg.
6. Assemble: Spread apple filling evenly over warm crust. Sprinkle reserved crumb topping over apples.
7. Optional egg wash: Brush topping lightly with beaten egg for extra golden shine.
8. Bake 35–40 minutes, until topping is golden and apples are tender.
9. Cool completely in pan on a wire rack before slicing into bars. Dust with powdered sugar or cinnamon sugar if desired.

💡 Pro Tips:
– Finely dice apples so they cook through and bars hold their shape.
– For extra flakiness, chill the pressed crust 15 minutes before par-baking.
– Store in an airtight container at room temp up to 2 days or refrigerate for longer freshness.

Prep Time & Nutrition (per bar, makes 16):