Butter a 10-cup bundt pan generously and stick it in the freezer while you prepare the cake batter (this will help the cake release from the pan easier later). Preheat oven to 350° F.
In a bowl, whisk together flour, spices, salt, and baking soda.
In a separate bowl, whisk together eggs, melted butter, sour cream, sugars, vanilla, and squash purée.
Gently fold the dry ingredients into the wet ingredients with a silicone spatula, mixing just until combined. Pour batter into prepared bundt pan and smooth it out until batter is evenly distributed.
Bake until golden brown, baked through, and cake starts to pull away from the edges of the pan slightly, about 50-60 minutes. Allow to cool.
Once cool, invert cake onto a plate and remove pan.