Preheat oven to 350 degrees F.
Liberally grease bundt or tube pan with cooking spray.
In a large bowl with electric mixer, combine egg whites, cream of tartar, salt, lemon zest, and vanilla and beat on high with whisk attachment until stiff peaks form.
With beater on low, add sugar and mix until combined.
Sprinkle flour on top and fold in.
Pour into prepared baking dish and bake in preheated oven for 33-38 minutes, until it is golden on top and it springs back when touched.
Cool completely.