Preheat the oven to 350
In a large, oven-proof skillet, heat the butter or olive oil over medium heat.
Add the diced asparagus and onions to the skillet and saute for 2 minutes until soft and tender. Add the tomatoes, dill and parsley to the skillet and cook for one minute.
Whisk the eggs and milk until frothy. Add the feta cheese to the egg mixture and pour into the skillet.
Cook the frittata on the stove over medium heat until the bottom is set – about 6-7 minutes. Do not stir or shake.
Carefully transfer the skillet to the oven and bake for 10 minutes until the frittata is firm and cooked all the way through.
Garnish with additional dill and sliced cherry tomatoes, feta, and microgreens if desired. Serve right away.