Blend the batter in a blender until smooth.
In a large nonstick pan, heat the oil over medium.
Saute the minced shallot for 5 minutes, or until soft. Be careful not to burn.
Meanwhile, chop the woody ends off of the asparagus and compost. Cut the asparagus tips off, then slice the stalks into rounds.
Saute the asparagus tips and rounds for 30 seconds, then remove the tips for garnish. Add the spinach, and cook for another 30 seconds. Season.
Spread the veggies evenly around the pan, then pour in the batter. Cover, and cook for about 5 minutes over medium heat, or until the bottom of the omelet is golden brown and the top is dry.
Slide the omelet onto a large plate, then place another plate on top, and flip, so that the cooked/browned side of the omelet is facing up. Slide the omelet back onto the pan so that the uncooked side can brown. Cover and cook for 3 more minutes, or until cooked through.
Slide the omelet back onto the plate, fold in half, then top with arugula, lemon juice, herbs, and hot sauce, if you wish.