Preheat oven to 350 degrees F. Butter an 8x8 cake pan and set aside.
In a stand mixer or with a hand mixer, cream together butter and sugars on high speed for 2 minutes until fluffy. Add egg and vanilla and mix until blended. Sift in dry ingredients, mixing until just incorporated.
Pour batter into prepared pan and spread evenly. Set aside.
Combine all ingredients in a large bowl and toss to coat. Allow to sit for 10 minutes, then arrange evenly on top of batter.
Stir together oats, sugar, flour, and spice in a small bowl. Cut in butter and massage in until mixture is crumbly. Spread evenly over the top of the apples.
Bake for 30-40 minutes in preheated oven until blondies are golden and a toothpick inserted in the center comes out cleanly with no batter.
Cool 5-10 minutes before serving, then enjoy with a drizzle of caramel or a scoop of ice cream.
Amount Per Serving
Calories387kcalCalories from fat 148
% Daily Value
Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs: