Preheat oven to 400°F. If not already, thaw your puff pastry to room temperature. Roll out & add pastry sheet to parchment paper lined sheet pan. Prick the pastry with a fork or pick evenly around the surface area. Bake on middle oven rack 5-8 minutes until edges turn slightly golden. Remove & set aside.
In a pan, boil your asparagus in about 1/2 - 3/4 inch of water 3-4 minutes. Remove from heat, drain hot water, then run the asparagus under cold water immediately to stop cooking (blanch).
In a mixing bowl, add your eggs, cream & green onion - whip together. Fold in your shredded cheeses. Add some garlic powder & a few pinches each salt & pepper - mix.
Smother the baked pastry tart with your egg-cheese mixture, leaving ½-¾ inch border/crust. Lay out your asparagus spears, drizzle with a bit of olive oil & sprinkle a few pinches grated Parmigiano-Reggiano cheese evenly over top.
Bake on middle oven rack 400°F for about 10 minutes, then turn temp to BROIL setting and broil about 5 mins (until cheese bubbles golden). Remove from oven & let sit about 5 mins. Sprinkle a bit of lemon zest over top. Cut into small squares with a pizza cutter & serve as an appetizer, on a brunch board or as a side to your favourite salad! Delish!