1. Preheat the oven to 350°F. Line a 9-inch cake pan with a round of parchment paper and spray with cooking spray.
2. In a large bowl, whisk together the flour, cinnamon, baking soda, salt, baking powder, and turmeric (if using).
3. In another large bowl, whisk the eggs, brown sugar, and sour cream together until well blended. Add the carrots and dates and, using a spatula or wooden spoon, mix until all the bits are evenly dispersed. Pour the wet ingredients into the dry ingredients and use a spatula to mix until just combined. Add the melted butter along with the oil and stop mixing as soon as you’ve got a nice, even batter.
4. Pour the batter into the prepared cake pan and bake until the top is puffed and golden and the sides pull away from the pan, 40–45 minutes.
5. This cake can be eaten now, or, for what I think is the optimal carrot cake experience, refrigerate it until completely chilled before slicing.
6. To make the frosting, combine softened cream cheese, powdered sugar, and a good pinch of kosher salt together in a medium bowl. Use a fork to combine everything (this is why the cream cheese needs to be at room temperature) until smooth, like softened butter. Spread onto the cake and sprinkle with chopped, toasted nuts if you like.