Preheat your oven to 350°F (175°C). Core and slice the apples uniformly.

Toss the sliced apples with a splash of lemon juice.

Melt butter in a skillet over medium heat, stirring until browned, about 5-8 minutes.

Combine rolled oats, all-purpose flour, brown sugar, and salt in a bowl. Drizzle in the warm brown butter and mix until crumbly.

Spread the apple mixture evenly in a baking dish and sprinkle the streusel topping over it.

Bake for approximately 45 minutes until topping is golden and apples are tender.

Let cool for 10-15 minutes before serving.