Set the oven to 350°F.

Heat cast iron pan on the oven on high, until it begins to smoke.

Meanwhile, whisk the eggs and half and half together and add salt and pepper.

Add 1 tablespoon of beef tallow to the pan and add all of the vegetables. Salt if desired. Cook on high heat until the vegetables are a little brown and crispy. Remove from pan.

Again, get the pan very hot and add the second tablespoon of beef tallow. Pour the egg mixture into the pan and turn off the heat.

Gently add the vegetables on top of the eggs on one half of the pan. Spread the cheese over all.

Move the pan into the oven and set the timer for 4 minutes, just enough time to melt the cheese and firm up the top surface of the eggs.

Remove the pan from the oven and use a spatula to fold the omelet to cover the vegetables.

Serve with sour cream and avocado slices.