Preheat oven to 350 degrees. Grease or line a 12 regular sized muffin pan with liners.
In a mixing bowl, sift together the flour, baking powder, salt, and pumpkin pie spice. Set aside.
In a large mixing bowl, whisk together the pumpkin, eggs, oil, vanilla, and brown sugar.
Slowly, add the dry ingredients into the bowl with all the wet ingredients. Mix well.
Spoon the batter into the muffin liners, about 3/4 of the way full.
To make the crumble mixture, combine the flour, sugar, and cinnamon in a small bowl. Add in the softened butter and use a fork or pastry fork to mix until crumbly.
Spoon Streusel mixture on top of muffins evenly. Bake in preheated oven for 18-20 minutes.
Let muffins cool in pan 5 minutes before removing them to continue to cool on a wire rack before enjoying!
