Preheat the oven to 375 degrees F. Line a muffin tin with liners.
Make the streusel first so it’s ready. Whisk together the sugar, cinnamon, salt and melted butter until combined. Whisk for a good minute or two until the sugar begins to dissolve, then use a wooden spoon to stir in the flour. The mixture will be crumb-like and dry. Almost like sludge or sand. This is what you want! Set it aside until you’re ready to use.
In a small bowl, whisk together the flour, baking soda, salt and pumpkin spice.
In a large bowl, whisk together the sugar and the eggs until combined. Whisk in the pumpkin puree. Whisk in the oil and vanilla extract until smooth.
Stir in the dry ingredients until just combined - do not overmix!
Fill the muffin tins about ½ of the way full. Sprinkle some of the streusel on top, then add another scoop of batter on top, filling them ¾ of the way full. Sprinkle the remaining streusel over the top of each. Bake the muffins for 20 to 22 minutes, or until set in the center. Let cool before serving!