Ingredients get added quickly to the frittata, so make sure your ingredients are prepped

Heat a large cast iron skillet on the stove on medium heat and drizzle with olive oil. Add the slices of potatoes into the skillet next by arranging just one layer of them. You may need to work in batches. Season all over with salt, pepper and spray directly with the cooking spray.

After potatoes are sizzling, cook for 2-3 minutes and then flip. Cook for another 2-3 minutes. They should be brown and crispy. Take them out of the pan and set aside.

Preheat oven to 340 degrees Fahrenheit.

Cut the breakfast sausage into bite sized pieces. Keep the pan on medium heat, Add the sausage and cook for about 5 minutes, moving around frequently. Add the diced onion and continue cooking until they start to brown, stirring frequently.

Prepare the eggs: whisk together 1 dozen eggs, half and half, salt and pepper.

Lay half of the potato slices back into the pan and create an even base. Pour the scrambled egg mix on top of everything. Add the rest of the potatoes, diced tomatoes, spinach, and cheese.

When the edges of the skillet start to cook, transfer to the oven and cook for 20-25 minutes. The middle may be a little jiggly, but will continue to cook after you take it out.

Cut into slices and serve immediately. If prepping in advance, reheat slices in the oven or microwave.