Preheat oven to 425 degrees.
Heat extra virgin olive oil in a cast iron skillet over medium heat.
Add the sausage to the pan and brown. Once the sausage is cooked, remove it from the pan and set aside.
If necessary, add more oil to the skillet. Add broccoli and cook 1-2 minutes, or until it browns on the edges. Remove and set aside.
Add the sliced onion to the pan and cook until softened and translucent. Remove and set aside.
In a large bowl, add the eggs and heavy cream. Whisk together and season with salt and pepper.
Pour the eggs into the skillet and cook for about 5 minutes.
As the eggs start to cook, add the sausage, baby broccoli, onion, sun-dried tomatoes, and feta cheese.
Cook frittata 18 minutes, or until frittata is puffy, center is cooked through, and edges are golden brown.
Allow the frittata to cool slightly before serving. Then, cut into slices.