Preheat the oven to 350°F (180°C). Line a 12-hole muffin pan with muffin paper liners. Slightly oil the paper with cooking oil spray. Set aside.
In a mixing bowl, whisk all-purpose flour, sugar, baking soda, and baking powder.
Fold in oil, pumpkin puree, apple sauce, pumpkin spices, and finely diced, peeled apples. Stir with a rubber spatula to incorporate and form a thick, smooth batter.
Use a cookie dough scoop to grab the muffin batter and release it into each muffin paper liner. Set aside.
In a mixing bowl, stir all the crumb topping ingredients. Use your fingertips to rub everything together and form a paste.
Crumble on top of each muffin, press a little to stick to the muffin batter.
Bake the muffins on the center rack of the oven for 28-35 minutes at 350°F (180°C) until a toothpick inserted in the center comes out clean.
Let the muffins cool down for 10 minutes in the pan, at room temperature, then on a cooling rack for 3 hours before eating,
