In a large nonstick sauté pan, heat the olive oil and butter over medium heat until the oil begins to shimmer. Add the red onion and cook, stirring occasionally, until softened and caramelized, about 30 minutes.
Preheat the oven to 350 degrees F. Coat a 9-inch ovenproof nonstick pan with nonstick spray.
Add the green onions and garlic to the caramelized onion and cook for 2 minutes. Stir in the spinach and cook until the leaves begin to wilt, 2 minutes. Add the cilantro, parsley, chives, dill and pine nuts, season with salt and pepper and remove from the heat. Transfer to the prepared pan and put in the oven for 5 minutes.
Meanwhile, in a blender, blend the eggs and milk on low for about 30 seconds. Pour the eggs over the veggie mixture in the pan, return to the oven and bake until puffed, just set and lightly golden brown on top, about 20 minutes.
Remove the omelet and let cool for 5 minutes on a baking rack. Transfer to a platter, slice into wedges and top with the yogurt.