Preheat oven to 400 degrees F. Heat olive oil in a 12-inch cast iron skillet over medium high heat.
Add spiralized beets and diced onions. Stir to coat vegetables in the olive oil, and saute for 7-10 minutes or until onions and beets are tender.
While the vegetables are cooking, add eggs, salt and pepper to a blender. Blend on low for 30 to 45 seconds or until the eggs are uniform. Do not blend the eggs on anything higher than a low setting.
Pour the egg mixture over the beets and onions, and "cook" over the burner for 1-2 minutes or until the eggs set at the bottom. Sprinkle the goat cheese on top, and press the crumbles into the egg mixture.
Bake for 20-25 minutes or until the eggs are cooked through. Let the frittata cool for a few minutes before serving.