Apple-Oatmeal Muffins

Preheat the oven to 350 degrees F (175 degrees C). Line 18 muffin cups with paper liners.

Combine brown sugar, all-purpose flour, and 1/2 teaspoon cinnamon in a small bowl; press in butter using the back of a spoon or your fingers until crumbly. Set topping aside.

Toss apples with lemon juice in a large bowl. Stir in white sugar, honey, buttermilk, oil, eggs, and vanilla until combined. Fold in oats.

Combine whole wheat flour, baking powder, 2 teaspoons cinnamon, baking soda, nutmeg, and salt in a small bowl; gently fold into apple-buttermilk mixture until just combined. Divide batter among the prepared muffin cups; top with crumb topping.

Bake in the preheated oven until tops spring back when lightly pressed, 20 to 25 minutes. Cool on a wire rack.