Preheat oven to 425°F. Take pumpkin and cut off the top and bottom. Slice in half and scoop out the insides, reserving seeds for roasting if you want. Dice into ½" cubes. Toss with olive oil and season with salt and pepper. Roast for 20 minutes, or until tender, flipping halfway through.
In a 12" cast iron skillet, heat butter over medium heat. Add onion and cook for about 5 minutes or until translucent. Add the garlic and sage, cooking for another minute. Toss in the roasted pumpkin.
While cooking onion, whisk together eggs with the heavy cream, salt and nutmeg. Stir in the goat cheese. Add egg mixture to skillet and cook until bottom begins to set, about 5 minutes.
Reduce oven to 375°F. Transfer skillet to oven and cook for another 15-20 minutes, or until top is set. Remove from oven and top with some additional sage if desired.
Notes
Whisk the eggs until the yolks and whites are fully combined, but avoid overmixing, which can make the frittata tough.
Don’t mess with the egg to dairy ratio or you won’t get the right consistency.
Cast iron skillets are the only way to go for a frittata. Don’t consider anything else.
You know the frittata is done when the center is slightly jiggly and the edges are golden brown.
Allow the frittata to rest for a few minutes before slicing and serving. This helps it set and makes it easier to cut into clean portions.