This omelet is great right out of the oven, but also makes great leftovers at room temperature. Slideshow: More Spaghetti Recipes
In a large heavy oven-proof skillet, heat the oil over medium heat until hot. Stir in the garlic, 1/2 teaspoon each salt and pepper, and cook, stirring occasionally, until the garlic is golden, about 2 minutes. Stir in the spinach and cook, turning with tongs, until the spinach is wilted, about 4 minutes. Remove the skillet from the heat.
Preheat the oven to 400°F.
In a large pot of boiling salted water, cook the spaghetti until al dente. Drain the pasta then toss in the skillet with the spinach mixture.
Whisk together the eggs, sour cream, 1/2 teaspoon salt and 1/4 teaspoon pepper, then pour over the spaghetti mixture in the skillet.
Bake the omelet until the eggs are set, about 20 minutes. Serve hot or at room temperature.