Preheat Oven to 350 F (177 C), and oil or grease a 9 inch pie pan.

In large frying pan, cook bacon slices until done, remove from pan, and chop bacon into chunks.

Pour off all but 1 tbsp of the bacon grease in the pan. Reduce heat to medium low and add chopped onion to pan with bacon grease.

Cook onion until softened and tender, for about 15 minutes.

In a large mixing bowl combine: 3 egg yolks, pumpkin puree, heavy cream, dried rosemary, sea salt, black pepper, nutmeg, sage, and the bacon onion mixture from the fry pan. Mix thoroughly.

In a Stand mixer or mixing bowl with electric hand mixer, beat 3 egg whites and optional cream of tartar until stiff peaks form.

Fold stiff egg whites into the yolk pumpkin mixture.

Spoon into prepare pie pan. Bake for about 35 minutes or until filling is set and center has risen. Cool for 5 minutes and serve.