In a medium bowl, beat the egg and salt together until smooth.
Place the onions in the egg mixture and stir gently to coat the onions and separate into rings.
In a separate medium bowl, mix together the cream of tartar, pork rind panko and parmesan cheese.
Using a fork, remove onions from egg mixture, letting excess drip off before placing the onions into the panko mixture. Repeat until all onions are added and toss gently to coat.
Spray or lightly coat a baking sheet with coconut oil.
Shake excess coating from onions and place in a single layer on the baking sheet.
Cook until lightly browned and tender, about 30 minutes, tossing the onions once about halfway through.
Remove onions from the oven and set aside to cool.
Reduce oven heat to 400°F.
Prepare the green beans while the onions are cooking. Bring a large stockpot of water to a boil
While the onions are cooking, prepare the beans. Bring a gallon of water and 2 tablespoons of salt to a boil in an 8-quart saucepan. Add the beans and blanch for 5 minutes. Drain in a colander and immediately plunge the beans into a large bowl of ice water to stop the cooking. Drain and set aside.
Lightly coat a 1 to 1 1/2 quart casserole dish with coconut oil or butter.
In a large bowl, mix together the green beans, cream of mushroom soup and a quarter of the crispy onions. Place the mixture into the casserole dish and top with the rest of the onions.
Place the beans into the oven and bake until bubbly, about 15 minutes.
Carbs in this recipe are from the green beans and onions. If you'd like to reduce carbs even more, consider a smaller serving of green beans. However, I find carbs from low carb, whole food vegetables don't generally affect ketosis.