Preheat oven to 320°F/160°C.
In a large bowl, whisk together brown sugar, oil, and eggs until well combined. Stir in tahini.
Add the two types of flour, baking powder, baking soda, salt, cinnamon, and nutmeg, mix just until a uniform mixture is obtained.
Fold in grated carrots.
Line muffin tins with paper liners and coat with cooking spray.
Fill each cup halfway to the top.
Bake for about 25-30 minutes. Test the center with a toothpick, if it comes out with a few moist crumbs, the muffins are done. If not, continue to bake until cooked through. Do not over-bake.
Allow the muffins to cool for 10 minutes in the muffin pan, then transfer to a wire rack to continue cooling.