1.Spray a 9x5 loaf pan with cooking spray. Preheat the oven to 350. In a large mixing bowl, whisk together sweet potato, olive oil, brown sugar, maple syrup, sour cream, eggs, and vanilla. The batter will likely have bits of sweet potato lumps throughout which is perfectly fine.
2.Now whisk in the baking soda, spices, and salt. Once incorporated, whisk in the flour. Pour the batter into your loaf pan. Bake for 50-60 minutes. Allow the loaf to cool, then make the meringue.
3.In a stand mixer with the whisk attachment, add the egg white and cream of tartar. Whip on high speed until it turns opaque and frothy (about 2 minutes).
4.Slowly pour in the sugar with the mixer still running. Whisk on high speed until you reach a thick marshmallowy consistency (about 5 minutes).
5.Mix in the vanilla. Spread the meringue over the cooled loaf and use a kitchen torch to toast the top.