Preheat oven to 400F. Prepare the streusel topping by combining the flour, sugar, and cinnamon in a small bowl, then cut in the butter with a fork until clumpy crumbles form. Set aside.

Beat together the wet ingredients plus the sugar. When they are completely combined, add in the baking powder, salt, and cinnamon. Mix again and then beat in the flour, just until combined.

Lightly spray a muffin tin with cooking spray and spoon in the muffin batter. Evenly distribute the streusel topping over each muffin, pressing the topping in lightly to keep it from rolling off when you move the tin.

Place the muffins in the oven and reduce the temperature to 375F. Bake for 22-24 minutes, until the muffins are golden brown. Cool for 10 minutes then enjoy, or allow to cool completely before storing in an airtight container.