Preheat oven to 375 F.
In 6-inch, oven-safe skillet over medium heat, melt butter. Add asparagus and cook 2-3 minutes.
In bowl, whisk eggs, cream, dill, salt, cheese and pepper. Pour egg mixture over asparagus.
Allow sides to set. Check by gently pulling egg away from side of skillet. Sides should appear cooked and become firm.
Top eggs with green onion and tomatoes. Place skillet in oven. Bake about 5 minutes until center of frittata is set and firm.
Remove from oven and plate while warm. Top with microgreens, if desired.