Tear six 18-inch sheets of aluminum foil.
Combine olive oil and pepper flakes in small bowl to make chili oil; microwave 30 seconds on high.
Cut lime to squeeze
Season both sides of the filets with salt (or garlic salt) and pepper to taste.
To assemble each packet, layer ingredients in this order in middle of foil sheet:
1½ cup lightly packed spinach leaves.
6 asparagus spears.
Filet.
1/6 of the sliced onions.
1 tablespoon chili oil.
1/6 of the lime juicJuice from 1 lime quarter.
Bring ends of foil together over food and crimp several times; crimp ends to close packet.
Bake in 450 degree oven for 12-15 minutes