Preheat oven to 400°F. Cut one large rectangular sheet of parchment paper.
Place lemon, lime, and orange slices in the center of the parchment sheet (slightly overlapping). Add fish fillet on top of the citrus slices. Sprinkle ½ teaspoon of salt, and ½ tablespoon of butter over the fish fillets. Stack the asparagus spears, cherry tomatoes, and squash on top. Season veggies with remaining salt, black pepper, a drizzle of extra-virgin olive oil, and top with a few sprigs of fresh herbs.
Bring the long sides of the paper together, and fold the top edges down to create a 1-in seal, then continue to fold down tightly over the fish and vegetables. Twist the open ends of the parchment in opposite directions to prevent steam from escaping. Place parchment packet on a sheet pan or an oven-proof pan and bake for 12-15 minutes.
Let packet stand for 5 minutes. Using sharp scissors, cut an X into the parchment and carefully cut open. Finish with a sprinkle of fresh chopped herbs and a squeeze of fresh lemon juice. Enjoy!
